OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..50
Eric Weisstein's World of Mathematics, Barbell Graph
Eric Weisstein's World of Mathematics, Edge Cover
FORMULA
MATHEMATICA
b[n_] := Sum[(-1)^(n-k)*Binomial[n, k]*2^Binomial[k, 2], {k, 0, n} ];
a[n_] := b[n]^2 + (b[n] + b[n - 1])^2;
Array[a, 13] (* Jean-François Alcover, Dec 27 2017, after Andrew Howroyd *)
PROG
(PARI) \\ here b(n) is A006129(n)
b(n)={ sum(k=0, n, (-1)^(n-k)*binomial(n, k)*2^binomial(k, 2)) }
a(n)={ b(n)^2 + (b(n) + b(n-1))^2 } \\ Andrew Howroyd, Dec 24 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Dec 23 2017
EXTENSIONS
a(1)-a(2) and terms a(7) and beyond from Andrew Howroyd, Dec 24 2017
STATUS
approved