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Search: id:A133230
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| A133230 |
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Largest index-sum i+j such that prime(i)+prime(j)=4*n^2. a(0)=-1 to indicate that there is no such pair of primes. |
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2
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| -1, 2, 8, 15, 22, 31, 41, 53, 63, 77, 90, 105, 123, 138, 157, 175, 194, 215, 237, 259, 281, 306, 330, 355, 382, 410, 437, 468, 498, 527, 558, 588, 623, 656, 689, 727, 762, 797, 836, 872, 911, 952, 992, 1033, 1076, 1119, 1161, 1205, 1249, 1294, 1341, 1390, 1434, 1483, 1534, 1585, 1634, 1687, 1738, 1791, 1842, 1898
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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a(n)= max(i+j), 1<=i<=j: A000040(i)+A000040(j)=A016742(n). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 22 2008
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MAPLE
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A133230 := proc(n) local a016742, i, j, a ; a016742 := 4*n^2 ; a := -1 ; if n =0 then RETURN(-1) ; fi ; for i from 1 to numtheory[pi](a016742-1) do if isprime(a016742-ithprime(i)) then j := numtheory[pi](a016742-ithprime(i)) : a := max(a, i+j) ; fi ; od: RETURN(a) ; end: seq(A133230(n), n=0..80) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 22 2008
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CROSSREFS
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Cf. A000040, A005843, A016742, A113631, A133229.
Sequence in context: A065907 A031272 A063286 this_sequence A077598 A095298 A100596
Adjacent sequences: A133227 A133228 A133229 this_sequence A133231 A133232 A133233
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KEYWORD
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sign
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AUTHOR
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Alexander R. Povolotsky (pevnev(AT)juno.com), Dec 19 2007
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EXTENSIONS
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Edited and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 22 2008
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