login
A024391
2nd elementary symmetric function of the first n+1 positive integers congruent to 2 mod 3.
5
10, 66, 231, 595, 1275, 2415, 4186, 6786, 10440, 15400, 21945, 30381, 41041, 54285, 70500, 90100, 113526, 141246, 173755, 211575, 255255, 305371, 362526, 427350, 500500, 582660, 674541, 776881, 890445, 1016025, 1154440, 1306536, 1473186, 1655290
OFFSET
1,1
FORMULA
a(n) = n*(n+1)*(3*n+2)*(3*n+5)/8.
O.g.f.: -x*(10+16*x+x^2)/(-1+x)^5 . - R. J. Mathar, Feb 14 2008
MATHEMATICA
LinearRecurrence[{5, -10, 10, -5, 1}, {10, 66, 231, 595, 1275}, 50] (* Harvey P. Dale, Aug 19 2019 *)
CROSSREFS
Sequence in context: A269679 A211056 A269468 * A074362 A080421 A320817
KEYWORD
nonn,easy
STATUS
approved