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A279231
Expansion of g.f. 1/((1 - x)^2*(1 - 3*x + 3*x^2)).
2
1, 5, 15, 34, 62, 90, 91, 11, -231, -716, -1444, -2172, -2171, 17, 6579, 19702, 39386, 59070, 59071, 23, -177123, -531416, -1062856, -1594296, -1594295, 29, 4782999, 14348938, 28697846, 43046754, 43046755, 35, -129140127, -387420452, -774840940, -1162261428
OFFSET
0,2
FORMULA
a(n) = 5*a(n-1) - 10*a(n-2) + 9*a(n-3) - 3*a(n-4) for n > 3.
a(n) = 3*a(n-1) - 3*a(n-2) + n + 1, with a(-1) = a(-2) = 0.
a(n) = 4 + n + 3^(1+n/2)*(sqrt(3)*sin(n*Pi/6) - cos(n*Pi/6)). - Stefano Spezia, Feb 11 2023
PROG
(PARI) Vec(1/((1-x)^2*(1-3*x+3*x^2)) + O(x^30)) \\ Colin Barker, Dec 08 2016
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Philippe Deléham, Dec 08 2016
EXTENSIONS
Incorrect term corrected by Colin Barker, Dec 09 2016
STATUS
approved