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A124274
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Nonprime numbers n that divide A124271[n] = Sum[ (Prime[i]^n - 1) / (Prime[i] - 1), {i,1,n} ].
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4
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OFFSET
| 1,2
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COMMENTS
| The next term if it exists is greater than 1000. A124271[n] = Sum[ (Prime[i]^n - 1) / (Prime[i] - 1), {i,1,n} ]. Note that a(1) = 1, a(2) = 3^2 and a(4) = 11^2 are the perfect squares. Primes p that divide A124271[p] are listed in A124273[n] = {3,7,13,17,19,31,47,59,61,71,101,103,107,109,137,149,151,157,167,197,...}.
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EXAMPLE
| A124271[n] begins {1,7,51,611,19839,603331,32981935,1469991559,108336139407,...}.
Thus a(1) = 1, a(2) = 9 because 9 divides A124271[9] = 108336139407, but all k do not divide A124271[k] for 1<k<9.
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CROSSREFS
| Cf. A124271, A124272, A124273, A124275, A123855, A123856.
Sequence in context: A136354 A177184 A098146 * A075134 A158789 A100241
Adjacent sequences: A124271 A124272 A124273 * A124275 A124276 A124277
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KEYWORD
| bref,hard,more,nonn
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AUTHOR
| Alexander Adamchuk (alex(AT)kolmogorov.com), Oct 23 2006
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