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Search: id:A061572
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| A061572 |
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(n!)^2*Sum(1/(k^2*(k-1)!),k=1..n). |
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+0
2
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| 1, 5, 47, 758, 18974, 683184, 33476736, 2142516144, 173543847984, 17354385161280, 2099880608143680, 302382807612606720, 51102694487009537280, 10016128119460096327680, 2253628826878608852019200, 576928979680925173791283200, 166732475127787396148470732800
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,100
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FORMULA
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Recurrence: a(1) = 1, a(2) = 5, a(n) = (n^2+n-1)*a(n-1) - (n-1)^3*a(n-2) for n >= 3. The sequence b(n) = n!^2 also satisfies this recurrence with the initial conditions b(1) = 1 and b(2) = 4. Hence we have the finite continued fraction expansion a(n)/b(n) = 1/(1-1^3/(5-2^3/(11-...-(n-1)^3/(n^2+n-1)))). Lim n -> infinity a(n)/b(n) = Ei(1) - gamma = 1/(1-1^3/(5-2^3/(11-...-(n-1)^3/(n^2+n-1)-...))). Cf. A061573. - Peter Bala (pbala(AT)toucansurf.com), Jul 10 2008
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PROGRAM
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(PARI) { for (n=1, 100, write("b061572.txt", n, " ", n!^2*sum(k=1, n, 1/(k^2*(k-1)!))) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 24 2009]
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CROSSREFS
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Cf. A061573.
Sequence in context: A098799 A089155 A086555 this_sequence A140422 A145564 A159480
Adjacent sequences: A061569 A061570 A061571 this_sequence A061573 A061574 A061575
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), May 19 2001
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