OFFSET
1,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..100
Eric Weisstein's World of Mathematics, Complete Tripartite Graph
Eric Weisstein's World of Mathematics, Matching
Eric Weisstein's World of Mathematics, Maximal Independent Edge Set
MATHEMATICA
Table[3 n! HypergeometricPFQ[{(1 - n)/2, -n, -n/2}, {1}, -4] - If[Mod[n, 2] == 0, 2 (n!/(n/2)!)^3, 0], {n, 20}]
PROG
(PARI) a(n)={if(n%2==0, binomial(n, n/2)*(n/2)!, 0)^3 + sum(k=0, (n-1)\2, 3*binomial(n, k)^2*binomial(n, 2*k)*binomial(2*k, k)*k!^2*(n-k)!)} \\ Andrew Howroyd, Dec 30 2017
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Eric W. Weisstein, Dec 30 2017
EXTENSIONS
Terms a(6) and beyond from Andrew Howroyd, Dec 30 2017
STATUS
approved