A026042 a(n) = (d(n)-r(n))/5, where d = A026040 and r is the periodic sequence with fundamental period (4,0,4,3,4).

4, 8, 12, 19, 28, 40, 56, 74, 97, 124, 156, 194, 236, 285, 340, 402, 472, 548, 633, 726, 828, 940, 1060, 1191, 1332, 1484, 1648, 1822, 2009, 2208, 2420, 2646, 2884, 3137, 3404, 3686, 3984, 4296, 4625, 4970, 5332, 5712, 6108, 6523, 6956, 7408, 7880, 8370, 8881, 9412, 9964, 10538, 11132, 11749

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,1,-3,3,-1).

Crossrefs

A152856 [From Richard Choulet, Dec 14 2008]

Formula

a(n)=(n + 4)*(n^2 + 5*n + 18)/15 - 3/5 - (1/2 - 3/10*5^(1/2))/5*cos(2*n*Pi/5) + (1/10*(4*(5 + 5^(1/2))^(1/2) - (5 - 5^(1/2))^(1/2))*2^(1/2))/5*sin(2*n*Pi/5) - (3/10*5^(1/2) + 1/2)/5*cos(4*n*Pi/5) + (1/10*((5 + 5^(1/2))^(1/2) + 4*(5 - 5^(1/2))^(1/2))*2^(1/2))/5*sin(4*n*Pi/5) [From Richard Choulet, Dec 14 2008]

G.f. x*( 4-4*x+3*x^3-x^4-3*x^5+5*x^6-2*x^7 ) / ( (x^4+x^3+x^2+x+1)*(x-1)^4 ). - R. J. Mathar, Jun 22 2013