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A117762 a(1)=6; for n>1, a(n) = prime(n)*(prime(n)^2-1)/2. 2
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

Table of n, a(n) for n=1..35.

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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Last modified February 7 08:09 EST 2016. Contains 268050 sequences.