21574

Appears in sequences

• a(n) = a(n-1) + a(n - 1 minus the number of terms of a(k) == n (mod 3) so far).at n=43A060730
• Fifth subdiagonal in array of n-gonal numbers A081422.at n=27A081436
• Poincaré series [or Poincare series] (or Molien series) for a certain four-fold wreath product P_4.at n=51A091434
• Triangular array: T(n,k) counts upper triangular matrices with entries from {0,1} having n 1's in total, with k 1's on the main diagonal and at least one nonzero entry in each row.at n=31A182319
• L.g.f.: Sum_{n>=1} a(n)*x^n/n = Sum_{n>=1} x^n/n * exp( Sum_{k>=1} sigma(n*k)*x^(n*k)/k ).at n=19A203321
• Number of self-inverse permutations p on [n] with displacement of elements restricted by 7: |p(i)-i| <= 7.at n=11A239079
• Numbers n such that n*2^2203 - 1 is prime.at n=26A265503
• Breadth-first traversal of a binary tree in which the value at the n-th node is equal to ParentNode()*prime(n-1).at n=19A268878
• a(0) = 1, a(n) = (denominator of the Bernoulli number B_{2n})/3, for n>=1.at n=33A277087
• Number of edges in a Farey fan of order n.at n=47A360043
• Products k of 4 distinct primes (or tetraprimes) such that k has no squarefree neighbors.at n=31A364141
• Products k of 4 distinct primes (or tetraprimes) such that none of k-2, k-1, k+1 and k+2 is squarefree.at n=12A364766