A026055 a(n) = (d(n)-r(n))/2, where d = A026054 and r is the periodic sequence with fundamental period (1,0,0,0).

6, 14, 25, 40, 59, 84, 114, 150, 192, 242, 299, 364, 437, 520, 612, 714, 826, 950, 1085, 1232, 1391, 1564, 1750, 1950, 2164, 2394, 2639, 2900, 3177, 3472, 3784, 4114, 4462, 4830, 5217, 5624, 6051, 6500, 6970, 7462, 7976, 8514, 9075, 9660, 10269, 10904, 11564, 12250, 12962, 13702, 14469, 15264

Offset: 3

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

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

Programs

Mathematica

LinearRecurrence[{3,-3,1,1,-3,3,-1},{6,14,25,40,59,84,114},60] (* Harvey P. Dale, Mar 27 2013 *)

Formula

a(n) = - 0.125 - 0.125*( - 1)^n - 0.25*cos(n*Pi/2) + (n + 2)*(n + 3)*(n + 13)/12 [From Richard Choulet, Dec 13 2008]

a(n) = (n + 2)*(n + 3)*(n + 13)/12 - 0.125 - 0.125*( - 1)^n - 0.25*cos(n*Pi/2) [From Richard Choulet, Dec 13 2008]

G.f.: x^3*( 6-4*x+x^2+x^3+6*x^5-2*x^6-6*x^4 ) / ( (1+x)*(x^2+1)*(x-1)^4 ). - R. J. Mathar, Jun 22 2013