20168

Appears in sequences

• a(n) = n + n*(n-1)*(n-2)*(n-3)*(n-4)*(n-5).at n=8A001096
• Expansion of Product_{k>=1} (1 - x^k)^(-k^2).at n=11A023871
• [ (4th elementary symmetric function of S(n))/(2nd elementary symmetric function of S(n)) ], where S(n) = {first n+3 positive integers congruent to 1 mod 3}.at n=16A024223
• a(n) = [ 2nd elementary symmetric function of {sqrt(k+1)} ], k = 1,2,...,n.at n=42A025219
• 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 71.at n=26A031569
• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 71.at n=1A031749
• E.g.f.: log(-1/(-1+x))^2 / (-1 + log(-1/(-1+x)))^2.at n=6A052865
• Triangle read by rows: T(n,k) = Sum_{j=0..k-1} T(n,j) + Sum_{j=1..n-k} T(n-j,k), with T(0,0)=1 and T(n,k) = 0 for k > n.at n=40A059450
• a(n) = (1/3!)*(n^3 + 24*n^2 + 107*n + 90), compare A059604.at n=42A059605
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 0, 1), (1, -1, 1), (1, 0, 0), (1, 1, -1)}.at n=10A148203
• Number of 3-step self-avoiding walks on an n X n square summed over all starting positions.at n=41A188148
• Number of nX7 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 0 and 1 1 1 vertically.at n=3A207894
• T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 0 and 1 1 1 vertically.at n=48A207895
• Number of 4Xn 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 0 and 1 1 1 vertically.at n=6A207897
• Define a square array B(m,n) (m>=0, n>=0) by B(n, n) = A212196(n)/A181131(n), B(n, n+1) = -A212196(n)/A181131(n), B(m, n) = B(m, n-1) + B(m+1, n-1); a(n) = numerator of B(0,n).at n=14A240776
• Number of partitions p of n such that the number of numbers having multiplicity 1 in p is not a part and the number of numbers having multiplicity > 1 is a part.at n=45A241415
• Number of connected subgraphs of the 12 X 12 grid graph induced by a vertex subset of size n.at n=6A262245
• Number of perfect matchings on a Möbius strip of width 3 and length 2n.at n=5A263200
• Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-2)*b(n), where a(0) = 2, a(1) = 4, b(0) = 1, b(1) = 3, b(2) = 5, and (a(n)) and (b(n)) are increasing complementary sequences.at n=14A296270
• Number of prime parts in the partitions of n into 7 parts.at n=47A309436