Sequences

One fifth of octo-factorial numbers.

One sixth of octo-factorial numbers.

Odd primes p such that q = (k*p+1)/(p-k) is prime for some p/2 < k < p.

Odd primes p such that q=(k*p+1)/(p-k) is prime for some k.

Primes of the form p^k - p + 1 for prime p.

31752-hyperperfect numbers: n = 31752*(sigma(n)-n-1) + 1.

Minimal determinant (negated) of n X n persymmetric matrix with entries {-1,0,+1}.

Maximal determinant of n X n persymmetric matrix with entries {-1,0,+1}.

Minimal consecutive determinant (negated) of n X n persymmetric matrix with entries {-1,0,+1}.

Maximal consecutive determinant of n X n persymmetric matrix with entries {-1,0,+1}.

Number of different determinants of n X n persymmetric matrices with entries {-1,0,+1}.

Numbers k such that 17^k - 16 is prime.

Numbers k such that 43^k - 42 is prime.

Numbers k such that 47^k-46 is prime.

Numbers k such that 89^k-88 is prime.

Numbers k such that 101^k-100 is prime.

Number of letters in "What is the next number in this sequence?".

Triangle of ballot numbers.

A triangle of Motzkin ballot numbers, read by rows.

Triangle, read by rows, formed by reading Pascal's triangle (A007318) mod 8.

Triangle read by rows: Pascal's triangle (A007318) mod 4.

Triangle, read by rows, formed by reading Pascal's triangle (A007318) mod 16.

Expansion of theta_3(q)^2 * theta_3(q^3) in powers of q.

Numbers k such that (3*k + 1)/2 is prime.

Successive approximations to 5-adic integer sqrt(-1).

Numbers k such that 3*k + 4 is prime.

Primes p of the form 6k-1 such that 2*p + 3 is prime.

Primes p such that (p-3)/2 is a prime of the form 6k-1.

a(n) is smallest number such that a(n)^2 + 1 is divisible by 5^n.

Number of rooted labeled triangular cacti with 2n+1 nodes (n triangles).

Number of labeled triangular cacti with 2n+1 nodes (n triangles).

Binomial transform of A002054.

Binomial transform of Padovan sequence A000931.

Successive approximations to 13-adic integer sqrt(-1).

Successive approximations to 7-adic integer sqrt(2).

Successive approximations to 11-adic integer sqrt(3).

Jacobi (or Kronecker) symbol (-1/n).

Decimal expansion of 1/9801.

Expansion of eta(8z)*eta(16z)*theta_3(z).

Expansion of eta(8z)*eta(16z)*theta_3(2z).

Expansion of eta(8z)*eta(16z)*theta_3(2z)*theta_3(4z).

Expansion of eta(16z)^4*eta(4z)^2.

Triangular numbers (A000217) with prime indices.

Odd triangular numbers with prime indices.

Even triangular numbers with prime indices.

Divide natural numbers in groups with prime(n) elements and add together.

Divide natural numbers in groups with prime(n) elements and add together.

Divide primes into groups with prime(n) elements and add together.

Divide even numbers into groups with prime(n) elements and add together.

Divide odd numbers into groups with prime(n) elements and add together.