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Search: id:A139224
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| 3, 21, 465, 8001, 33542145, 8589737985, 137438167041, 2305843005992468481, 2658455991569831742348849606740148225, 191561942608236107294793377465333618488307184098607105
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OFFSET
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1,1
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COMMENT
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Perfect number A000396(n) minus Mersenne prime A000668(n).
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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)=A000668(n)*(A000668(n)-1)/2. Also a(n)=A000396(n)-A000668(n).
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CROSSREFS
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Cf. A000217, A000396, A000668, A036689, A139096, A139115, A139116, A139223, A139225, A139226, A139256, A139306.
Sequence in context: A108716 A084620 A120603 this_sequence A032469 A006927 A014375
Adjacent sequences: A139221 A139222 A139223 this_sequence A139225 A139226 A139227
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KEYWORD
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nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), May 10 2008
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EXTENSIONS
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More terms from Max Alekseyev (maxale(AT)gmail.com), Mar 09 2009
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