A026038 a(n) = (d(n)-r(n))/2, where d = A026037 and r is the periodic sequence with fundamental period (1,0,0,1).

5, 11, 20, 33, 52, 78, 111, 152, 203, 265, 338, 423, 522, 636, 765, 910, 1073, 1255, 1456, 1677, 1920, 2186, 2475, 2788, 3127, 3493, 3886, 4307, 4758, 5240, 5753, 6298, 6877, 7491, 8140, 8825, 9548, 10310, 11111, 11952, 12835, 13761, 14730, 15743, 16802, 17908, 19061, 20262, 21513, 22815, 24168

Offset: 3

Author

Clark Kimberling

Keywords

• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (4,-7,8,-7,4,-1).

Formula

G.f. x^3*( 5-9*x+11*x^2-10*x^3+7*x^4-2*x^5 ) / ( (x^2+1)*(x-1)^4 ). - R. J. Mathar, Jun 22 2013