OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (7, -21, 35, -35, 21, -7, 1).
FORMULA
a(n) = (n^6 - n^3 - n^2 + n)/6.
From Colin Barker, Dec 08 2017: (Start)
G.f.: x^2*(9 + 53*x + 47*x^2 + 11*x^3) / (1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.
(End)
PROG
(PARI) concat(0, Vec(x^2*(9 + 53*x + 47*x^2 + 11*x^3) / (1 - x)^7 + O(x^40))) \\ Colin Barker, Dec 08 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric M. Schmidt, Dec 08 2017
STATUS
approved