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Search: id:A065824
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| A065824 |
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Smallest solution m to (n+1)*Phi[m] = n*Sigma[m], or -1 if no solution exists. |
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+0
2
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| 3, 5, 7, 323, 11, 13, 899, 17, 19, 1763, 23, 5249, 3239, 29, 31, 979801, 5459, 37, 10763, 41, 43, 9179, 47, 9701, 10403, 53, 12319, 5646547, 59, 61, 24569, 19109, 67, 19043, 71, 73, 22499, 50819, 79, 41309, 83, 32639, 46979, 89, 34579, 39059, 125969
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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(n+1)*A000010(a[n])=n*A000203(a[n]), smallest x=a[n] solutions
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EXAMPLE
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If p = a[n] is a prime solution, then (n+1)(p-1) = n(p+1) and p = 2n+1, so position for p if it is in fact a minimal solution is at n = (p-1)/2. E.g. 29 appears at 14th position shown by A005097. On the other hand large and (seemingly always composite) solutions arise at indices shown essentially by A047845. Also, differences between the sites of two consecutive small prime solutions appears to be d/2, half the difference between consecutive primes (A001223).
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CROSSREFS
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Cf. A000010, A000203, A062699, A065818, A065819, A065822, A065823
See also A005097, A047845, A014076, A001223.
Sequence in context: A082756 A068832 A046472 this_sequence A069463 A073691 A110336
Adjacent sequences: A065821 A065822 A065823 this_sequence A065825 A065826 A065827
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KEYWORD
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nice,nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Nov 23 2001
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