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A054620
Number of ways to color vertices of a pentagon using <= n colors, allowing only rotations.
4
0, 1, 8, 51, 208, 629, 1560, 3367, 6560, 11817, 20008, 32219, 49776, 74269, 107576, 151887, 209728, 283985, 377928, 495235, 640016, 816837, 1030744, 1287287, 1592544, 1953145, 2376296, 2869803, 3442096, 4102253, 4860024
OFFSET
0,3
FORMULA
a(n) = (n^5+4*n)/5 = n*(n^2-2*n+2)*(n^2+2*n+2)/5.
G.f.: x*(1+2*x+18*x^2+2*x^3+x^4) / (x-1)^6 . - R. J. Mathar, Aug 30 2011
a(n) = -a(-n). - Bruno Berselli, Aug 31 2011
PROG
(Magma) [(n^5+4*n)/5: n in [0..40]]; // Vincenzo Librandi, Aug 31 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Apr 16 2000
STATUS
approved