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Search: id:A115560
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| A115560 |
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x and x+2 are here they are twin prime numbers and the square of both are present in A115557. |
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+0
3
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| 11, 13, 29, 31, 197, 199, 239, 241, 419, 421, 659, 661, 881, 883, 1019, 1021, 1061, 1063, 1481, 1483, 1877, 1879, 3167, 3169, 3821, 3823, 4019, 4021, 4049, 4051
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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The commutator[sigma, tau] is zero and a(n) is the square root of special prime solutions. These solutions are twin primes. Both twins are displayed.
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PROGRAM
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ta={{0}}; tb={{0}}; Do[s=DivisorSigma[1, DivisorSigma[0, n]]; s1=DivisorSigma[0, DivisorSigma[1, n]]; If[Equal[s-s1, 0]&&IntegerQ[Sqrt[n]&&PrimeQ[Sqrt[n]]], Print[n]; ta=Append[ta, n]; tb=Append[tb, Sqrt[n]]], {n, 1, 100000000}] ta=Delete[ta, 1]; tb=Delete[tb, 1]; ni=Intersection[tb, 2+tb]; Union[ni, ni-2]
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CROSSREFS
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Cf. A000005, A000203, A076360, A076361, A062068, A062069, A115557, A115558, A115559.
Sequence in context: A132245 A117314 A140567 this_sequence A045466 A107645 A106014
Adjacent sequences: A115557 A115558 A115559 this_sequence A115561 A115562 A115563
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana1.sote.hu), Jan 25 2006
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