OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,3,-1,-3,-1).
FORMULA
G.f.: x*(1 + x - x^2)/((1 + x)*(1 - x - x^2)^2). - Andrew Howroyd, Sep 21 2025
EXAMPLE
a(4) = 9 = (3 + 3 + 2 + 2), sum of row 4 of A131336.
PROG
(PARI) Vec((1 + x - x^2)/((1 + x)*(1 - x - x^2)^2) + O(x^40)) \\ Andrew Howroyd, Sep 21 2025
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson, Jun 29 2007
EXTENSIONS
a(11) onwards from Andrew Howroyd, Sep 21 2025
STATUS
approved