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Search: id:A139328
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| 0, 3, 6, 10, 14, 19, 24, 30, 36, 45, 52, 60, 67, 76, 86, 96, 105, 117, 127, 138, 151, 162, 176, 189, 203, 216, 230, 246, 262, 277, 292, 308, 325, 343, 362, 376, 398, 417, 435, 451, 473, 491, 515, 535, 557, 579, 599, 622, 646, 668, 691, 712, 737, 764, 788, 815
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OFFSET
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1,2
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COMMENT
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a(n) = Sum(A139325(n,k): 1<=k<=n).
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FORMULA
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a(n) = A000720(2*n^2 - 1) - 1.
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EXAMPLE
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a(4)=#{3,5,7}+#{11,13}+#{17,19,23}+#{29,31}}=3+2+3+2}=10:
..1 ...3 ...5 ...7 ... primes in 1st row = {3,5,7},
..9 ..11 ..13 ..15 ... primes in 2nd row = {11,13},
.17 ..19 ..21 ..23 ... primes in 3rd row = {17,19},
.25 ..27 ..29 ..31 ... primes in 4th row = {29,31}.
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CROSSREFS
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Cf. A038107.
Sequence in context: A130246 A167381 A036572 this_sequence A134919 A033437 A024928
Adjacent sequences: A139325 A139326 A139327 this_sequence A139329 A139330 A139331
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 14 2008
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