OFFSET
1,1
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
Index entries for linear recurrences with constant coefficients, signature (28,-322,1960,-6769,13132,-13068,5040).
FORMULA
a(n) = 15*7^n-45*6^n+65*5^n-55*4^n+28*3^n-8*2^n+1.
G.f.: -3*x*(1680*x^6 -3976*x^5 +3946*x^4 -1807*x^3 +451*x^2 -57*x+3) / ((x -1)*(2*x -1)*(3*x -1)*(4*x -1)*(5*x -1)*(6*x -1)*(7*x -1)). - Colin Barker, Feb 22 2015
EXAMPLE
a(8) = 32857101.
MAPLE
f:=n->15*7^n-45*6^n+65*5^n-55*4^n+28*3^n-8*2^n+1;
PROG
(PARI) Vec(-3*x*(1680*x^6 -3976*x^5 +3946*x^4 -1807*x^3 +451*x^2 -57*x+3) / ((x -1)*(2*x -1)*(3*x -1)*(4*x -1)*(5*x -1)*(6*x -1)*(7*x -1)) + O(x^100)) \\ Colin Barker, Feb 22 2015
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Aleksandar M. Janjic and Milan Janjic, Feb 04 2007
STATUS
approved