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 (21,-175,735,-1624,1764,-720).
FORMULA
a(n) = 16*6^n-40*5^n+44*4^n-26*3^n+8*2^n-1.
G.f.: -x*(720*x^5-1764*x^4+1412*x^3-591*x^2+112*x-9) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)*(6*x-1)). - Colin Barker, Feb 22 2015
EXAMPLE
a(8) = 13963901.
MAPLE
f:=n->16*6^n-40*5^n+44*4^n-26*3^n+8*2^n-1;
MATHEMATICA
LinearRecurrence[{21, -175, 735, -1624, 1764, -720}, {9, 77, 633, 5021, 38409, 283277}, 30] (* Harvey P. Dale, Oct 14 2016 *)
PROG
(PARI) Vec(-x*(720*x^5-1764*x^4+1412*x^3-591*x^2+112*x-9)/((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)*(6*x-1)) + O(x^100)) \\ Colin Barker, Feb 22 2015
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Aleksandar M. Janjic and Milan Janjic, Feb 08 2007
STATUS
approved