OFFSET
1,1
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Antelope Graph
Eric Weisstein's World of Mathematics, Clique
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = 5*n^2-28*n+49 for n >= 3.
From Colin Barker, Jun 10 2019: (Start)
G.f.: x*(2 - x + x^2 + 8*x^4) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>5.
(End)
MATHEMATICA
Table[Piecewise[{{2, n == 1}, {5, n == 2}}, 49 - 28 n + 5 n^2], {n, 20}]
PROG
(PARI) Vec(x*(2 - x + x^2 + 8*x^4) / (1 - x)^3 + O(x^50)) \\ Colin Barker, Jun 10 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Jun 09 2019
STATUS
approved