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Search: id:A133229
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| A133229 |
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Smallest 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, 14, 20, 27, 37, 46, 57, 70, 80, 95, 108, 124, 142, 160, 174, 193, 213, 231, 253, 277, 297, 321, 346, 376, 396, 425, 451, 476, 507, 537, 566, 598, 626, 659, 693, 725, 770, 796, 836, 870, 912, 941, 984, 1022, 1060, 1103, 1146, 1187, 1243, 1277, 1322, 1366, 1404, 1449, 1500, 1553, 1597, 1648, 1691, 1746, 1798
(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)= min(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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A133229 := proc(n) local a016742, i, j, a ; a016742 := 4*n^2 ; a := 2*numtheory[pi](a016742) ; 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 := min(a, i+j) ; fi ; od: RETURN(a) ; end: seq(A133229(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, A133230.
Adjacent sequences: A133226 A133227 A133228 this_sequence A133230 A133231 A133232
Sequence in context: A082933 A016933 A101959 this_sequence A046940 A046939 A082930
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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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