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A007407
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Denominator of Sum 1/k^2, k=1..n.
(Formerly M3661)
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31
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1, 4, 36, 144, 3600, 3600, 176400, 705600, 6350400, 1270080, 153679680, 153679680, 25971865920, 25971865920, 129859329600, 519437318400, 150117385017600, 150117385017600, 54192375991353600, 10838475198270720, 221193371393280
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| D. Y. Savio, E. A. Lamagna and S.-M. Liu, Summation of harmonic numbers, pp. 12-20 of E. Kaltofen and S. M. Watt, editors, Computers and Mathematics, Springer-Verlag, NY, 1989.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..200
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FORMULA
| a(n) = Denominator of (Pi^2)/6 - Zeta[2, x] [From Artur Jasinski (grafix(AT)csl.pl), Mar 03 2010]
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MAPLE
| ZL:=n->sum(1/i^2, i=2..n): a:=n->floor(denom(ZL(n))): seq(a(n), n=1..21); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 28 2007
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MATHEMATICA
| s=0; lst={}; Do[s+=n^2/n^4; AppendTo[lst, Denominator[s]], {n, 3*4!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Jan 24 2009]
Table[Denominator[Pi^2/6 - Zeta[2, x]], {x, 1, 22}] [From Artur Jasinski (grafix(AT)csl.pl), Mar 03 2010]
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CROSSREFS
| Cf. A007406.
Sequence in context: A103931 A068589 A120077 * A051418 A069046 A065886
Adjacent sequences: A007404 A007405 A007406 * A007408 A007409 A007410
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KEYWORD
| nonn,easy,frac,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein
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