A024391 2nd elementary symmetric function of the first n+1 positive integers congruent to 2 mod 3.

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

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).

Programs

Mathematica

LinearRecurrence[{5,-10,10,-5,1},{10,66,231,595,1275},50] (* Harvey P. Dale, Aug 19 2019 *)

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