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Search: id:A008864
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| 3, 4, 6, 8, 12, 14, 18, 20, 24, 30, 32, 38, 42, 44, 48, 54, 60, 62, 68, 72, 74, 80, 84, 90, 98, 102, 104, 108, 110, 114, 128, 132, 138, 140, 150, 152, 158, 164, 168, 174, 180, 182, 192, 194, 198, 200, 212, 224, 228, 230, 234, 240, 242, 252, 258, 264, 270, 272, 278, 282, 284
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Number of divisors of 2^p = p+1 = A000005[A034785(n)] = A000203[A000040(n)] = Sum of divisors of primes. - Labos E. (labos(AT)ana.sote.hu), May 24 2001
a(n) = A084920(n)/A006093(n). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 06 2007
Or, three together with nonprime numbers k such that k-1 is prime. - Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Sep 08 2009
Also, the sum of trivial divisors of nth prime . - Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Sep 26 2009
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REFERENCES
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C. W. Trigg, Problem #1210, Series Formation, J. Rec. Math., 15 (1982), 221-222.
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MATHEMATICA
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Table[Prime[n]+1, {n, 1, 30}] - Vladimir Orlovsky, Apr 27 2008
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CROSSREFS
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a(n) = p(n)+1 = A000040(n)+1=A000040(n)+A000012(n).
Cf. A000040, A060800, A131991, A131992, A131993, A141468.
Sequence in context: A050115 A167711 A037346 this_sequence A129295 A049305 A147606
Adjacent sequences: A008861 A008862 A008863 this_sequence A008865 A008866 A008867
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), R. K. Guy
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