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
Keywords
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