A317976 - OEIS

A317976

a(n) = 2*(a(n-1)+a(n-2)+a(n-3))-a(n-4) for n >= 4, with initial terms 0,0,1,0.

0, 0, 1, 0, 2, 6, 15, 46, 132, 380, 1101, 3180, 9190, 26562, 76763, 221850, 641160, 1852984, 5355225, 15476888, 44729034, 129269310, 373595239, 1079710278, 3120420620, 9018182964, 26063032485, 75323561860, 217689133998, 629133273722, 1818228906675, 5254779066930, 15186593360656, 43890069394800, 126844654738097

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,5

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (2,2,2,-1).

FORMULA

G.f.: x^2*(1 - 2*x) / (1 - 2*x - 2*x^2 - 2*x^3 + x^4). - Colin Barker, Sep 09 2018

MATHEMATICA

(See A192235.)

PROG

(PARI) concat(vector(2), Vec(x^2*(1 - 2*x) / (1 - 2*x - 2*x^2 - 2*x^3 + x^4) + O(x^40))) \\ Colin Barker, Sep 09 2018