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Search: id:A000114
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| A000114 |
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Number of cusps of principal congruence subgroup GAMMA^{hat}(n). |
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+0
2
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| 3, 4, 6, 12, 12, 24, 24, 36, 36, 60, 48, 84, 72, 96, 96, 144, 108, 180, 144, 192, 180, 264, 192, 300, 252, 324, 288, 420, 288, 480, 384, 480, 432, 576, 432, 684, 540, 672, 576, 840, 576, 924, 720, 864, 792, 1104, 768
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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A001766(n)=n*a(n). - Michael Somos Jan 29 2004
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REFERENCES
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R. A. Rankin, Modular Forms and Functions, Cambridge 1977, p. 62.
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MAPLE
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A000114 := proc(n) local b, d: if n = 2 then RETURN(3); else b := n^2/2; for d from 1 to n do if irem(n, d) = 0 and isprime(d) then b := b*(1-d^(-2)); fi; od; RETURN(b); fi: end:
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CROSSREFS
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Adjacent sequences: A000111 A000112 A000113 this_sequence A000115 A000116 A000117
Sequence in context: A002090 A062822 A113728 this_sequence A136243 A051592 A044843
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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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