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 A007687 Number of 4-colorings of cyclic group of order n. (Formerly M2833) 2
 3, 10, 21, 44, 83, 218, 271, 692, 865, 2622, 2813, 9220, 9735, 35214, 35911, 135564, 136899 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The number of 2-colorings of Z_n is A000034(n-1), the number of 3-colorings of Z_n is A005843(n). It seems that the number of n-colorings of Z_2 is A137928(n-1). - Andrey Zabolotskiy, Oct 02 2017 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. Haas, Three-colorings of finite groups or an algebra of nonequalities, Math. Mag., 63 (1990), 211-225. R. Hass, Letter to N. J. A. Sloane, Aug. 1994 PROG (Python) def colorings(n, zp):     result = 0     f = [0]*zp     for i in range(n**zp):         for j1 in range(zp):             for j2 in range(zp):                 if (f[j1]+f[j2])%n == f[(j1+j2)%zp]:                     break             else:                 continue             break         else:             result += 1         f[0] += 1         for j in range(zp-1):             if f[j] == n:                 f[j] = 0                 f[j+1] += 1     return result print([colorings(4, k) for k in range(1, 12)]) # Andrey Zabolotskiy, Jul 12 2017 CROSSREFS Cf. A007688. Sequence in context: A207380 A268348 A117495 * A192033 A295063 A298856 Adjacent sequences:  A007684 A007685 A007686 * A007688 A007689 A007690 KEYWORD nonn,more AUTHOR EXTENSIONS a(6)-a(11) from Andrey Zabolotskiy, Jul 12 2017 a(12)-a(17) from Andrey Zabolotskiy, Oct 02 2017 STATUS approved

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Last modified May 25 04:50 EDT 2019. Contains 323539 sequences. (Running on oeis4.)