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Search: id:A103729
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| 1, 5, 13, 41, 61, 113, 145, 221, 365, 421, 613, 761, 841, 1013, 1301, 1625, 1741, 2113, 2381, 2521, 2965, 3281, 3785, 4513, 4901, 5101, 5513, 5725, 6161, 7813, 8321, 9113, 9385, 10805, 11101, 12013, 12961, 13613, 14621, 15665, 16021
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OFFSET
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0,2
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COMMENT
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It is clear that the a(n) are natural numbers since only odd primes appear in the formula below.
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FORMULA
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a(n)=A103728(n+2, 2)=(1 + (p(n+2)-1)*binomial(p(n+2)-1, 2))/p(n+2), with p(n):=A000040(n) (n-th prime).
a(n)= (5 - 4*p(n+2) + p(n+2)^2)/2 = sum(A103718(k, m)*p(n+2)^m, m=0..2)/2.
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CROSSREFS
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Sequence in context: A121872 A025490 A087938 this_sequence A027862 A100210 A080267
Adjacent sequences: A103726 A103727 A103728 this_sequence A103730 A103731 A103732
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KEYWORD
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nonn,easy
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang_AT_physik_DOT_uni-karlsruhe_DOT_de), Feb 24 2005
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