A026047 a(n) = (d(n)-r(n))/2, where d = A026046 and r is the periodic sequence with fundamental period (0,1,0,1).

38, 52, 72, 97, 130, 170, 220, 279, 350, 432, 528, 637, 762, 902, 1060, 1235, 1430, 1644, 1880, 2137, 2418, 2722, 3052, 3407, 3790, 4200, 4640, 5109, 5610, 6142, 6708, 7307, 7942, 8612, 9320, 10065, 10850, 11674, 12540, 13447, 14398, 15392, 16432, 17517, 18650, 19830, 21060, 22339, 23670

Offset: 6

Author

Clark Kimberling

Keywords

• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (3,-2,-2,3,-1).

Formula

a(n)=(n + 6)*(n^2 + 6*n + 38)/6 - 0.5*sin(n*Pi/2)^2 [From Richard Choulet, Dec 13 2008]

G.f. x^6*( 38-62*x-8*x^2+61*x^3-27*x^4 ) / ( (1+x)*(x-1)^4 ). - R. J. Mathar, Jun 22 2013