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Search: id:A063532
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| A063532 |
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Numbers n such that both Phi[n]+1=x^2 and Sigma[n]+1=y^2 for some x and y. |
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+0
2
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| 15, 35, 56, 72, 78, 84, 123, 143, 165, 323, 543, 627, 678, 728, 814, 836, 899, 1350, 1484, 1535, 1683, 1763, 1846, 2296, 2967, 3288, 3444, 3599, 3784, 4103, 4620, 5084, 5183, 5964, 6580, 6693, 6820, 7150, 7626, 7806, 9096
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OFFSET
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1,1
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EXAMPLE
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If n = p(p+2) is a product of twin primes then Phi[n]+1=p^2, Sigma[n]+1=(p+2)^2, so n is in the sequence, A037074 a proper subset. There are many other solutions such as 72, 123, 165, etc.
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CROSSREFS
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Cf. A000010, A000203, A037074.
Adjacent sequences: A063529 A063530 A063531 this_sequence A063533 A063534 A063535
Sequence in context: A130871 A143202 A108668 this_sequence A090196 A067930 A098271
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Aug 02 2001
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