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Search: id:A001767
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| A001767 |
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Genus of modular group GAMMA_n. Or, genus of modular curve CHI(n).
(Formerly M2459 N0976)
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+0
1
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| 0, 0, 0, 0, 1, 3, 5, 10, 13, 26, 25, 50, 49, 73, 81, 133, 109, 196, 169, 241, 241, 375, 289, 476, 421, 568, 529, 806, 577, 1001, 833, 1081, 1009, 1393, 1081, 1768, 1441, 1849, 1633, 2451, 1729, 2850, 2281, 2809, 2641, 3773, 2689, 4215, 3301, 4321, 3865
(list; graph; listen)
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OFFSET
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2,6
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
R. C. Gunning, Lectures on Modular Forms. Princeton Univ. Press, Princeton, NJ, 1962, p. 15.
B. Iversen, Hyperbolic Geometry, Cambridge Univ. Press, 1992, see p. 238.
Russian Encyclopedia of Mathematics, Vol. 3, page 931.
B. Schoeneberg, Elliptic Modular Functions, Springer-Verlag, NY, 1974, p. 94.
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LINKS
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Index entries for sequences related to modular groups
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PROGRAM
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(PARI) {a(n)=if(n<3, 0, 1+n^2*(n-6)/24*prod(p=2, n, if(isprime(p)&(n%p==0), 1-1/p^2, 1)))} /* Michael Somos May 19 2004 */
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CROSSREFS
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Sequence in context: A031878 A160792 A137395 this_sequence A048214 A001841 A008610
Adjacent sequences: A001764 A001765 A001766 this_sequence A001768 A001769 A001770
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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