91520

Appears in sequences

• a(1) = 1, a(n) = Sum_{k=1..n-1} ((6^k - 1)/5)*a(k).at n=4A015507
• Expansion of (1+9*x)/(1-x)^11.at n=7A056114
• Number triangle T(n,k) = binomial(n,k)*binomial(2n,n-k).at n=37A110608
• a(n) = n * binomial(2*n, n-1).at n=8A110609
• Triangle T(n, k) = n!*Sum_{j=k..n} (-1)^(j+k)*binomial(k+j, j)/j!, read by rows.at n=53A156984
• Triangle T(n,k) = binomial(n,k)*binomial(n+k+1,n+1) read by rows, 0 <= k <= n.at n=43A178301
• Numbers with prime factorization pqrs^7.at n=27A190473
• Number of valleys in all left factors of Dyck paths of length n. A valley is a (1,-1)-step followed by a (1,1)-step.at n=17A191522
• Numbers k such that k = Product (p_j^e_j) = Product (p_j*(e_j + 1)).at n=31A304410