OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (6, -15, 20, -15, 6, -1).
FORMULA
G.f.: x*(1+456*x+5184*x^2+8102*x^3+2055*x^4+42*x^5) / (x-1)^6.
a(0) = 0, a(n) = 1+(10+(44+(110+(165+132*(n-1))*(n-1))*(n-1))*(n-1)) * (n-1) for n>0.
EXAMPLE
a(1) = 1: aaaaaaaaaaaa (with 1-ary alphabet {a}).
MAPLE
a:= n-> `if`(n=0, 0, (x-> 1+(10+(44+(110+(165+132*x)*x)*x)*x)*x)(n-1)):
seq(a(n), n=0..30);
MATHEMATICA
LinearRecurrence[{6, -15, 20, -15, 6, -1}, {0, 1, 462, 7941, 48838, 185193, 530526}, 30] (* Harvey P. Dale, Oct 23 2015 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Sep 02 2011
STATUS
approved