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Search: id:A061652
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| 2, 4, 16, 64, 4096, 65536, 262144, 1073741824, 1152921504606846976, 309485009821345068724781056, 81129638414606681695789005144064, 85070591730234615865843651857942052864
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OFFSET
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1,1
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COMMENT
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It is conjectured that there are no odd superperfect numbers, in which case this coincides with A019279.
The number of divisors of a(n) is equal to A000043(n). - Omar E. Pol (info(AT)polprimos.com), Feb 29 2008
The sum of divisors of a(n) is equal to A000668(n), the n-th Mersenne prime. - Omar E. Pol (info(AT)polprimos.com), Mar 11 2008
Largest proper divisor of A075398(n). - Omar E. Pol (info(AT)polprimos.com), Apr 25 2008
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REFERENCES
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G. L. Cohen and H. 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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Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Experimental Mathematics, Home Page
O. E. Pol, Determinacion geometrica de los numeros primos y perfectos".
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FORMULA
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a(n) = 2^(A090748(n)). - Lekraj Beedassy (boodhiman(AT)yahoo.com), Dec 07 2007
a(n)=(1 + A000668(n))/2. - Omar E. Pol (info(AT)polprimos.com), Mar 11 2008
a(n) = 2^A000043(n)/2 = A075398(n)/2 = A032742(A075398(n)). - Omar E. Pol (info(AT)polprimos.com), Apr 25 2008
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CROSSREFS
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Cf. A019279.
Cf. A000043.
Cf. A000668.
Cf. A032742, A075398.
Sequence in context: A060656 A061286 A019279 this_sequence A058926 A102736 A103619
Adjacent sequences: A061649 A061650 A061651 this_sequence A061653 A061654 A061655
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KEYWORD
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nonn,nice
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Jun 16 2001
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