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Search: id:A133028
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| A133028 |
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Perfect numbers divided by 2. |
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+0
16
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| 3, 14, 248, 4064, 16775168, 4294934528, 68719345664, 1152921504069976064, 1329227995784915872327346307976921088, 95780971304118053647396689042151819065498660774084608, 6582018229284824168619876730229361455111736159193471558891864064, 7237005577332262213973186563042994240786838745737417944533177174565599576064
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(13) has 314 digits and is too large to include. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 23 2007
Largest proper divisor of n-th perfect number.
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LINKS
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O. E. Pol, Determinacion geometrica de los numeros primos y perfectos.
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FORMULA
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a(n)=A000396(n)/2. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 23 2007
a(n) = 2^(A000043(n)-2) * A000668(n). - Omar E. Pol (info(AT)polprimos.com), Mar 01 2008
a(n) = A032742(A000396(n)).
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MAPLE
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a:=proc(n) if isprime(2^n-1)=true then 2^(n-2)*(2^n-1) else end if end proc: seq(a(n), n=1..120); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 24 2007
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CROSSREFS
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Cf. A028334. Perfect numbers: A000396.
Cf. A000043, A000668.
Cf. A018254, A018487, A032742, A133024, A133025, A135652, A135653, A135654, A135655.
Sequence in context: A058388 A081383 A001320 this_sequence A144985 A081397 A092987
Adjacent sequences: A133025 A133026 A133027 this_sequence A133029 A133030 A133031
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KEYWORD
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easy,nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), Oct 20 2007, Apr 23 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 23 2007
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