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A117762
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a(1) = 6; for n>1, a(n) = prime(n)*(prime(n)^2 - 1)/2.
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9
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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
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OFFSET
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1,1
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COMMENTS
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a(n) is the order of the matrix group PSL(2,prime(n)). - corrected by Tom Edgar, Sep 28 2015
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REFERENCES
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Blyth and Robertson, Essential Student Algebra, Volume 5: Groups,Chapman and Hall, New York, page 14
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LINKS
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FORMULA
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MATHEMATICA
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a[n_]= If[n==1, 6, Prime[n]*(Prime[n]^2 -1)/2];
Table[a[n], {n, 40}]
Join[{6}, Table[Prime[n] (Prime[n]^2 - 1)/2, {n, 2, 40}]] (* Vincenzo Librandi, Sep 29 2015 *)
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PROG
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(PARI) a(n) = prime(n)*(prime(n)^2-1)/2;
(Magma) [6] cat [NthPrime(n)*(NthPrime(n)^2-1)/2: n in [2..40]]; // Vincenzo Librandi, Sep 29 2015
(SageMath)
def A117762(n): return nth_prime(n)*(nth_prime(n)^2-1)/2 + 3*int(n==1)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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