OFFSET
0,5
LINKS
Michael De Vlieger, Table of n, a(n) for n = 0..93
Paul Barry, Centered polygon numbers, heptagons and nonagons, and the Robbins numbers, arXiv:2104.01644 [math.CO], 2021.
FORMULA
a(n) = A005130(n) - n!
MATHEMATICA
a[n_] := Product[(3 k + 1)!/(n + k)!, {k, 0, n-1}] - n!; a /@ Range[0, 17] (* Giovanni Resta, Nov 20 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Wendy Appleby, Nov 11 2018
STATUS
approved