OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Complete Bipartite Graph
Index entries for linear recurrences with constant coefficients, signature (5,-8,4).
FORMULA
a(n) = (2 + n)*2^(n-1) - 2.
From Colin Barker, Nov 05 2019: (Start)
G.f.: x*(1 + x - 4*x^2) / ((1 - x)*(1 - 2*x)^2).
a(n) = 5*a(n-1) - 8*a(n-2) + 4*a(n-3) for n>3.
(End)
PROG
(PARI) a(n) = {(2 + n)*2^(n-1) - 2}
(PARI) Vec(x*(1 + x - 4*x^2) / ((1 - x)*(1 - 2*x)^2) + O(x^30)) \\ Colin Barker, Nov 05 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Andrew Howroyd, Oct 29 2019
STATUS
approved