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Search: id:A139226
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| 1, 7, 155, 2667, 11180715, 2863245995, 45812722347, 768614335330822827, 886151997189943914116283202246716075, 63853980869412035764931125821777872829435728032869035, 4388012152856549445746584486819520216982214368341183846591146667, 4824670384888174809315457708695329493801178769338122219111555681805105015467
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Perfect number A000396(n) minus Mersenne prime A000668(n), divided by 3.
Terms from a(13) on have 313 or more digits and are not listed for that reason. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 11 2008
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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)/6 = A139223(n)/6 = A139224(n)/3. Also a(n)=(A000396(n)-A000668(n))/3.
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CROSSREFS
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Cf. A000217, A000396, A000668, A036689, A139096, A139115, A139116, A139223, A139224, A139225, A139256, A139306.
Adjacent sequences: A139223 A139224 A139225 this_sequence A139227 A139228 A139229
Sequence in context: A006761 A141835 A111831 this_sequence A073605 A115866 A009703
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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 R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 11 2008
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