A026068 - OEIS

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A026068

(d(n)-r(n))/5, where d = A026066 and r is the periodic sequence with fundamental period (0,3,1,0,1).

21, 33, 49, 68, 90, 116, 145, 179, 217, 259, 306, 357, 414, 476, 543, 616, 694, 779, 870, 967, 1071, 1181, 1299, 1424, 1556, 1696, 1843, 1999, 2163, 2335, 2516, 2705, 2904, 3112, 3329, 3556, 3792, 4039, 4296, 4563, 4841, 5129, 5429, 5740, 6062, 6396, 6741

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OFFSET

7,1

LINKS

Table of n, a(n) for n=7..53.

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

FORMULA

a(n)=(n + 7)*(n^2 + 35*n + 90)/30 - 1/5*(1 + ( - 1/2 + 3/10*5^(1/2))*cos(2*n*Pi/5) + (1/5*2^(1/2)*(5 + 5^(1/2))^(1/2) + 1/10*2^(1/2)*(5 - 5^(1/2))^(1/2))*sin(2*n*Pi/5) + ( - 1/2 - 3/10*5^(1/2))*cos(4*n*Pi/5) + ( - 1/10*2^(1/2)*(5 + 5^(1/2))^(1/2) + 1/5*2^(1/2)*(5 - 5^(1/2))^(1/2))*sin(4*n*Pi/5)) - Richard Choulet, Dec 14 2008

a(n)= 3*a(n-1) -3*a(n-2) +a(n-3) +a(n-5) -3*a(n-6) +3*a(n-7) -a(n-8). G.f.: -x^7*(-21+30*x-13*x^2+x^3+20*x^5-29*x^6+11*x^7)/( (x^4+x^3+x^2+x+1) * (x-1)^4). - R. J. Mathar, Oct 05 2009

MATHEMATICA

LinearRecurrence[{3, -3, 1, 0, 1, -3, 3, -1}, {21, 33, 49, 68, 90, 116, 145, 179}, 60] (* Harvey P. Dale, Sep 10 2014 *)

CROSSREFS

Cf. A152892.

Sequence in context: A279229 A339963 A141249 * A217263 A330441 A176945

Adjacent sequences: A026065 A026066 A026067 * A026069 A026070 A026071

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling

EXTENSIONS

Corrected by T. D. Noe, Dec 11 2006

STATUS

approved