67104

Appears in sequences

• Number of perfect matchings on an n X n L-shaped graph.at n=12A079472
• Number of derangements of [n] avoiding the patterns 123, 132 and 213.at n=24A114215
• Constant term in the reduction by (x^2 -> x+1) of the polynomial p(n,x) given in Comments.at n=13A192872
• Denominators a(n) of Pythagorean approximations b(n)/a(n) to 1/2.at n=11A195547
• Number of n X 3 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once.at n=5A269030
• 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=33A269035
• Number of 6 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once.at n=2A269040
• a(n) = a(n-1) + a(n-3) + a(n-4), where a(0) = 1, a(1) = 2, a(2) = 3, a(3) = 4.at n=23A293411
• a(n) = a(n-1) + a(n-3) + a(n-4), where a(0) = 0, a(1) = 0, a(2) = 0, a(3) = 2.at n=26A295680
• G.f. A(x) satisfies: R(x^2*A(x)) = x^3 - x^4, where R(A(x)) = x.at n=46A350433
• Triangle read by rows: T(n,k) is the number of unlabeled weakly connected oriented graphs with n arcs and k vertices, k = 1..n+1.at n=52A350914
• a(n) is the smallest integer k such that k is the sum of exactly n distinct permutations of k, all having the same number of digits as k.at n=5A384708