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Search: id:A019277
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| A019277 |
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Let sigma_m(n) be the result of applying the sum-of-divisors function m times to n; let m(n) = min m such that n divides sigma_m (n); let k(n) = sigma_{m(n)}(n)/n; sequence gives k(n) for the megaperfect numbers n, where m(n) increases. |
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+0
2
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| 1, 2, 4, 5, 7, 15, 16, 17, 78, 97, 101, 120, 174, 214, 239, 261, 263, 296, 380, 557, 1287, 1524, 1722, 1911, 2023, 2373
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Records in A019294. a(n>=23) depend on a few probable primes.
See also the Cohen-te Reile links under A019276.
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REFERENCES
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Graeme L. Cohen and Herman J. J. te Riele, Iterating the sum-of-divisors function, Experimental Mathematics, 5 (1996), pp. 93-100.
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LINKS
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Experimental Mathematics, Home Page
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MATHEMATICA
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f[n_, m_] := Block[{d = DivisorSigma[1, n]}, If[Mod[d, m] == 0, 0, d]]; g[n_] := Length[ NestWhileList[ f[ #, n] &, n, # != 0 &]] - 1; a = 0; Do[b = g[n]; If[b > a, a = b; Print[ a]], {n, 460}] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 24 2005)
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CROSSREFS
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Cf. A019276, A019294, A019295.
Sequence in context: A063508 A123210 A101724 this_sequence A127791 A005620 A049915
Adjacent sequences: A019274 A019275 A019276 this_sequence A019278 A019279 A019280
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KEYWORD
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hard,nonn
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AUTHOR
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njas
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