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Search: id:A023036
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| A023036 |
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Smallest positive even integer that is an unordered sum of two primes in exactly n ways. |
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+0
13
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| 2, 4, 10, 22, 34, 48, 60, 78, 84, 90, 114, 144, 120, 168, 180, 234, 246, 288, 240, 210, 324, 300, 360, 474, 330, 528, 576, 390, 462, 480, 420, 570, 510, 672, 792, 756, 876, 714, 798, 690, 1038, 630, 1008, 930, 780, 960, 870, 924, 900, 1134, 1434, 840, 990, 1302, 1080
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Except for a(1), the same as A001172.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..1000
Index entries for sequences related to Goldbach conjecture
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EXAMPLE
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a(3) = 22 as 22 = (19+3) = (17+5)= ( 11+11). There are exactly 3 ways 22 can be expressed as the sum of two primes, and no even number less than 22 can be so expressed.
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MATHEMATICA
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f[n_] := Block[{c = 0, k = 3}, While[k <= n/2, If[PrimeQ[k] && PrimeQ[n - k], c++ ]; k++ ]; c]; a = Table[0, {55}]; a[[1]] = 2; a[[2]] = 4; Do[b = f[n]; If[b < 55 && a[[b + 1]] == 0, a[[b + 1]] = n], {n, 6, 1500, 2}] (from Robert G. Wilson v Dec 20 2003)
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CROSSREFS
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Cf. A045917, A000954.
Sequence in context: A104431 A036954 A109679 this_sequence A075898 A005306 A091618
Adjacent sequences: A023033 A023034 A023035 this_sequence A023037 A023038 A023039
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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