20580

Appears in sequences

• Nearest integer to 4 * Pi * n^3 / 3.at n=17A002101
• Number of 3-voter voting schemes with n linearly ranked choices.at n=26A007009
• Place n distinguishable balls in n boxes (in n^n ways); let f(n,k) = number of ways that max in any box is k, for 1 <= k <= n; sequence gives f(n,n-2)/n.at n=12A019579
• a(n) = n*(n - 1)^3/2.at n=15A019582
• Numbers k such that the set of prime divisors of k is equal to the set of prime divisors of sigma(k).at n=13A027598
• a(n) = (11*n + 4)*C(n+3, 3)/4.at n=13A055268
• Number of 7-element ordered antichains on an unlabeled n-element set; T_1-hypergraphs with 7 labeled nodes and n hyperedges.at n=0A056073
• Saint-Exupéry numbers: ordered products of the three sides of Pythagorean triangles.at n=14A057096
• Number of 7-element ordered T_0-antichains on an unlabeled n-set; T_1-hypergraphs on 7 labeled nodes with n (not necessarily empty) distinct hyperedges (n=0,1,...,128).at n=5A059050
• Numbers k such that cototient(k) is a square and sets a new record for squares.at n=32A063753
• Smallest number with persistence n for the sort-and-subtract-sequence.at n=23A065641
• a(n) = number of unicyclic connected simple graphs whose cycle has length 4.at n=3A065889
• Number of 5-gonal compositions of n into positive parts.at n=31A069983
• a(n) = n*(2*n^2 -3*n +7)/6 = C(n, 1) + C(n, 2) + 2*C(n, 3).at n=39A081489
• Triangle T(n,k), read by rows, given by [0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, ...] DELTA [1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, ...] where DELTA is the operator defined in A084938.at n=49A089949
• Square of Narayana triangle A001263: View A001263 as a lower triangular matrix. Then the square of that matrix is also lower triangular. Sequence gives this lower triangle, read by rows.at n=31A095801
• Triangle T(n,k) of numbers of connected (unicyclic) graphs with unique cycle of length k (3<=k<=n), on n labeled nodes.at n=11A098909
• a(n) = C(2n-1,n-1) mod n^3.at n=37A099907
• a(n) = (n+1)(n+2)^2*(n+3)^3*(n+4)^2*(n+5)(n^2 + 6n + 10)/86400.at n=4A107917
• Intersection of A108027, A108028, A108029 and A108030.at n=9A108109