Problems

Browse reviewed problems by field, research program, status, and recorded activity.

50 of 2,322 problems shown

Problem	Field	Status	Latest contribution
Third-level log-concavity of the Riemann Xi kernel	Analytic number theory	Open	Submitted · 7d
The exact Erdős-Sárközy bound for property P	Number theory	Open	Submitted · 1d
A strengthened supercongruence for averaged Apéry numbers	Number theory	Open	Submitted · 1d
Surjectivity of a capped-step Recamán sequence	Number theory	Open	Submitted · 1d
Aligned hundred-integer blocks containing exactly 22 or 23 primes	Number theory	Open	Submitted · 2d
Integer return under the 4/3 ceiling map	Number theory	Open	Submitted · 1d
Polynomial-time recognition of squarefree and triangular-divisor-free integers	Number theory	Open	Submitted · 1d
A third noninitial prime in the fresh-remainder gcd sequence	Number theory	Open	Submitted · 1d
Does 387 occur in the self-describing digit-sum sequence?	Combinatorics	Open	Submitted · 1d
Further fixed points in the guarded gcd sequence	Number theory	Open	Submitted · 1d
Completeness of the four known loops in a prime-factor Collatz map	Number theory	Open	Submitted · 2d
Off-edge traps for the diagonally numbered greedy knight	Combinatorics	Open	Submitted · 2d
Universal weighted sums of eight fifth powers	Additive number theory	Open	Submitted · 2d
Trapping the origin-first three-dimensional knight walk	Graph theory	Open	Submitted · 2d
Perfect powers among the values pi(2^n)	Number theory	Open	Submitted · 1d
Harary-Hill crossing-number conjecture for complete graphs	Graph theory	Open	Submitted · 2d
Will the visible-prime Ulam walk ever visit 571?	Discrete dynamical systems	Open	Submitted · 1d
Triangular numbers with every even divisor count	Number theory	Open	Submitted · 1d
A prime of every length using only digits 1 and 2	Number theory	Open	Submitted · 2d
Prime digit sums using only 3 and 4	Number theory	Open	Submitted · 2d
The Eldar-Ordowski gcd criterion for Wolstenholme numerators	Number theory	Open	Submitted · 2d
Two last-exception descriptions for divisor counts of p^n minus 1	Number theory	Open	Submitted · 1d
Doubling law for rotated XOR cycle lengths	Combinatorics	Open	Submitted · 1d
Is 3291 the longest nonzero run in the reset process?	Number theory	Open	Submitted · 1d
Cutoff bounds for the least split prime	Number theory	Open	Submitted · 1d
Does the 1373 adjacent-digit-sum orbit ever cycle?	Number theory	Open	Submitted · 1d
Total definition of the six-seed Hofstadter Q relative	Integer sequences	Open	Submitted · 1d
Recursive generation of the partition-code order	Combinatorics	Open	Submitted · 1d
Global record gaps below fifth powers	Number theory	Open	Submitted · 1d
Universal translated containers for fixed polyominoes	Combinatorics	Open	Submitted · 1d
Prime values of Sophie Germain coefficient polynomials	Number theory	Open	Submitted · 1d
Three primes 1 modulo 4 summing to every later prime 3 modulo 4	Number theory	Open	Submitted · 1d
Persistent leading divisor-count classes in a feedback sequence	Combinatorics	Open	Submitted · 1d
Infinitely many shifted primes with power-of-two cofactors	Number theory	Open	Submitted · 1d
At least four primes between every two consecutive cubes	Number theory	Open	Submitted · 1d
Composite solutions of a totient-exponent congruence	Number theory	Open	Submitted · 1d
Nonexistence of odd superperfect numbers	Number theory	Open	Submitted · 1d
A factorial with exactly nine decimal 4s	Number theory	Open	Submitted · 1d
Regular Hadamard matrices of every even-square order	Combinatorics	Open	Submitted · 1d
Cycle or bi-infinite orbit through 6 in the prime-signature permutation	Number theory	Open	Submitted · 1d
Twin-prime-free intervals between prime-indexed primes	Number theory	Open	Submitted · 1d
Are all multiply-perfect numbers practical?	Number theory	Open	Submitted · 1d
Are all powers of two after 2^168 decimal-pandigital?	Number theory	Open	Submitted · 1d
An exact linear recurrence for the Pisot sequence T(5,8)	Number theory	Open	Submitted · 1d
Submultiplicativity of maximal permanents in the indecomposable 3-regular class	Combinatorics	Open	Submitted · 1d
A sqrt(2)/2 displacement bijection for rotated triangular lattices	Discrete geometry	Open	Submitted · 1d
Three conjectural zeros in a totient addition equation	Number theory	Open	Submitted · 1d
Symmetric three-term recurrences for sampled partial-map counts	Combinatorics	Open	Submitted · 1d
Infinitely many semiprimes of the form m squared plus one	Number theory	Open	Submitted · 1d
A prime-power supercongruence for products of Apery numbers	Number theory	Open	Submitted · 1d

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