OFFSET
1,4
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Halved Cube Graph
Eric Weisstein's World of Mathematics, Maximal Clique
Index entries for linear recurrences with constant coefficients, signature (8, -24, 32, -16).
FORMULA
a(n) = 2^(n - 4)*(n^2 - 5*n + 12)*(n + 2)/3 for n > 3.
a(n) = 8*a(n-1) - 24*a(n-2) + 32*a(n-3) - 16*a(n-4) for n > 7.
G.f.: x*(1 - 7*x + 17*x^2 - 64*x^4 + 112*x^5 - 64*x^6) / (1 - 2*x)^4. - Colin Barker, Dec 11 2017
MATHEMATICA
Table[If[n < 4, 1, 2^(n - 4) (n^2 - 5 n + 12) (n + 2)/3], {n, 12}]
Join[{1, 1, 1}, LinearRecurrence[{8, -24, 32, -16}, {16, 56, 192, 624}, 30]]
CoefficientList[Series[(1 - 7 x + 17 x^2 - 64 x^4 + 112 x^5 - 64 x^6)/(-1 + 2 x)^4, {x, 0, 20}], x]
PROG
(PARI) Vec(x*(1 - 7*x + 17*x^2 - 64*x^4 + 112*x^5 - 64*x^6) / (1 - 2*x)^4 + O(x^40)) \\ Colin Barker, Dec 11 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Dec 01 2017
STATUS
approved