21408

Appears in sequences

• Convolution of (F(2), F(3), F(4), ...) and primes.at n=15A023657
• Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 73.at n=28A031571
• Number of 3-step one or two space at a time rook's tours on an n X n board summed over all starting positions.at n=20A187288
• Let m_n denote the number which is obtained from n-base representation of m if its digits are written in nondecreasing order; then a(n) is the smallest period of the sequence which is defined by the recurrence b(0)=0, b(1)=1, b(k)=(b(k-1) + b(k-2))_n, for k>=2, or a(n)=0, if there is no such period.at n=47A237671
• T(n,k)=Number of nXk 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once.at n=37A269035
• Number of 2 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once.at n=7A269036
• Expansion of Product_{k>=1} (1 - k*x^k) / (1 + x^k).at n=33A269339
• Number of independent vertex sets and vertex covers in the n-web graph.at n=6A287485
• Solution of the complementary equation a(n) = a(0)*b(n-1) + a(1)*b(n-2) + ... + a(n-1)*b(0), where a(0) = 2, a(1) = 4, b(0) = 1, and (a(n)) and (b(n)) are increasing complementary sequences.at n=9A296003