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A082020
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Decimal expansion of 15/Pi^2.
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13
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1, 5, 1, 9, 8, 1, 7, 7, 5, 4, 6, 3, 5, 0, 6, 6, 5, 7, 1, 6, 5, 8, 1, 9, 1, 9, 4, 8, 1, 4, 5, 9, 1, 4, 5, 8, 3, 5, 6, 5, 3, 8, 1, 6, 2, 0, 0, 8, 3, 6, 9, 8, 2, 3, 2, 6, 8, 4, 1, 3, 5, 4, 7, 8, 4, 1, 2, 5, 9, 6, 8, 1, 4, 4, 3, 3, 5, 3, 1, 6, 1, 7, 8, 6, 8, 1, 3, 9, 1, 0, 8, 8, 8, 4, 3, 2, 7, 5, 6
(list; constant; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| S. Ramanujan, Irregular numbers, J. Indian Math. Soc., 5 (1913), 105-106; Coll. Papers 20-21.
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LINKS
| S. Ramanujan, Irregular numbers
Eric Weisstein's World of Mathematics, Prime Sums
Eric Weisstein's World of Mathematics, Moebius Function
Eric Weisstein's World of Mathematics, Prime Products
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FORMULA
| Product_{n >= 1} (1+1/prime(n)^2) = 15/Pi^2. - Ramanujan
a(n)=Zeta(2)/Zeta(4)=A013661/A013662=sum(n=1, Infinity, mu(n)^2/n^2)=sum(n=1, Infinity, |mu(n)|/n^2). - Enrique Pérez Herrero, Jan 15 2012
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EXAMPLE
| 1.51981775463506657...
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MATHEMATICA
| A082020[digits_] := First[RealDigits[Zeta[2]/Zeta[4], 10, digits]]; A082020[100] (* Enrique Pérez Herrero, Jan 15 2012 *)
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CROSSREFS
| Sequence in context: A154605 A114594 A021662 * A147406 A147354 A134233
Adjacent sequences: A082017 A082018 A082019 * A082021 A082022 A082023
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KEYWORD
| nonn,cons
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), May 09 2003
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