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 A117762 a(1)=6; for n>1, a(n) = prime(n)*(prime(n)^2-1)/2. 4
 6, 12, 60, 168, 660, 1092, 2448, 3420, 6072, 12180, 14880, 25308, 34440, 39732, 51888, 74412, 102660, 113460, 150348, 178920, 194472, 246480, 285852, 352440, 456288, 515100, 546312, 612468, 647460, 721392, 1024128, 1123980, 1285608, 1342740, 1653900 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is the order of the matrix group PSL(2,prime(n)). - corrected by Tom Edgar, Sep 28 2015 REFERENCES Blyth and Robertson, Essential Student Algebra, Volume 5: Groups,Chapman and Hall, New York, page 14 LINKS FORMULA a(n) = A127918(n), n>1. MATHEMATICA f[n_] = If[Prime[n] - 2 == 0, 6, Prime[n]*(Prime[n]^2 - 1)/2] a = Table[f[n], {n, 1, 25}] Join[{6}, Table[Prime[n] (Prime[n]^2 - 1)/2, {n, 2, 40}]] (* Vincenzo Librandi, Sep 29 2015 *) PROG (PARI) a(n) = prime(n)*(prime(n)^2-1)/2; vector(40, n, a(n+1)) \\ Altug Alkan, Sep 28 2015 (MAGMA) [6] cat [NthPrime(n)*(NthPrime(n)^2-1)/2: n in [2..40]]; // Vincenzo Librandi, Sep 29 2015 CROSSREFS Cf. A084920, A127918. Sequence in context: A033931 A228847 A093901 * A178957 A104362 A123900 Adjacent sequences:  A117759 A117760 A117761 * A117763 A117764 A117765 KEYWORD nonn,easy AUTHOR Roger L. Bagula, Apr 14 2006 EXTENSIONS More terms from Vincenzo Librandi, Sep 29 2015 STATUS approved

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