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Search: id:A124272
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| A124272 |
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Primes in A124271[n], or primes of the form Sum[ (Prime[i]^n - 1) / (Prime[i] - 1), {i,1,n} ]. |
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+0
5
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OFFSET
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1,1
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COMMENT
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A124271[n] = Sum[ (Prime[i]^n - 1) / (Prime[i] - 1), {i,1,n} ]. A124271[n] is prime for n = {2,8,14,...}.
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EXAMPLE
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A124271[n] begins {1,7,51,611,19839,603331,32981935,1469991559,...}.
Thus a(1) = 7 because A124271[2] = 7 is prime but A124271[1] = 1 is not prime.
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MATHEMATICA
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Do[f=Sum[(Prime[i]^n-1)/(Prime[i]-1), {i, 1, n}]; If[PrimeQ[f], Print[{n, f}]], {n, 1, 100}]
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CROSSREFS
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Cf. A124271, A124273, A124274, A124275, A123855, A123856.
Sequence in context: A116257 A075984 A109300 this_sequence A128820 A067485 A127886
Adjacent sequences: A124269 A124270 A124271 this_sequence A124273 A124274 A124275
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KEYWORD
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bref,hard,more,nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), Oct 23 2006
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