OFFSET
1,3
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (2,0,0,-2,-2,3,0,3,-2,-2,0,0,2,-1).
FORMULA
MATHEMATICA
LinearRecurrence[{2, 0, 0, -2, -2, 3, 0, 3, -2, -2, 0, 0, 2, -1}, {0, 1, 3, 7, 13, 25, 40, 65, 99, 146, 208, 294, 399, 538}, 50] (* Harvey P. Dale, Mar 06 2021 *)
PROG
(PARI) concat([0], Vec((1 + x + x^2 - x^3 + x^4 - 2*x^5 + 2*x^6)/((1 - x)^6*(1 + x)^2*(1 + x^2)*(1 + x + x^2)^2) + O(x^40)))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Andrew Howroyd, Oct 23 2019
STATUS
approved