26320

Appears in sequences

• Number of n-node rooted trees of height at most 3.at n=19A001383
• Number of rooted toroidal maps with 4 vertices and n faces and no isthmuses.at n=2A006427
• Number of noninvertible 2 X 2 matrices over Z/nZ (determinant is a divisor of 0).at n=12A020479
• Number of 2's in n-th term of A007651.at n=40A022467
• Number of ways to place two nonattacking queens on an n X n board.at n=15A036464
• a(n)=Sum{T(n,j): j=1,2,...,n}, array T given by A048201.at n=32A048209
• Numbers k such that 2^k - 1 is divisible by (k-1).at n=23A087965
• Triangle of coefficients of q in e.g.f. that satisfies: A(x,q) = exp( q*x*A(q*x,q) ), read by rows of [n*(n-1)/2 + 1] terms in row n for n>=0.at n=68A126265
• Number of (n+1)X(1+1) 0..2 arrays with the upper median plus the lower median minus the minimum of every 2X2 subblock equal.at n=5A236782
• Number of (n+1)X(6+1) 0..2 arrays with the upper median plus the lower median minus the minimum of every 2X2 subblock equal.at n=0A236787
• T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with the upper median plus the lower median minus the minimum of every 2X2 subblock equal.at n=15A236789
• T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with the upper median plus the lower median minus the minimum of every 2X2 subblock equal.at n=20A236789
• Number of (n+1)X(1+1) 0..3 arrays with the upper median plus the lower median of every 2X2 subblock equal.at n=3A237000
• Number of (n+1)X(4+1) 0..3 arrays with the upper median plus the lower median of every 2X2 subblock equal.at n=0A237003
• T(n,k) = Number of (n+1) X (k+1) 0..3 arrays with the upper median plus the lower median of every 2 X 2 subblock equal.at n=6A237007
• T(n,k) = Number of (n+1) X (k+1) 0..3 arrays with the upper median plus the lower median of every 2 X 2 subblock equal.at n=9A237007
• Positive numbers m such that m^2 - 1 divides 2^m - 1.at n=12A247219
• Positive numbers m such that m^2 - 1 divides 4^m - 1.at n=21A271842
• Triangle read by rows: T(n,k) is the number of rooted toroidal maps with n edges and k faces and without isthmuses, n >= 2, k = 1..n-1.at n=17A343092