OFFSET
1,1
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Clique
Eric Weisstein's World of Mathematics, Fiveleaper Graph
Wikipedia, Clique
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = 7*n^2 - 38*n + 49 for n > 4.
From Colin Barker, Jun 10 2019: (Start)
G.f.: x*(2 - x + x^2 + 8*x^4 + 12*x^5 - 8*x^6) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>7.
(End)
PROG
(PARI) Vec(x*(2 - x + x^2 + 8*x^4 + 12*x^5 - 8*x^6) / (1 - x)^3 + O(x^40)) \\ Colin Barker, Jun 10 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Jun 10 2019
STATUS
approved