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Search: id:A160994
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| A160994 |
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Least prime power having n divisors such that every sum of two or more divisors is composite. |
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+0
1
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| 3, 7, 7, 19, 19, 139, 151, 211, 211, 211, 421, 2311, 2311, 92401, 120121, 120121, 180181, 2312311
(list; graph; listen)
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OFFSET
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2,1
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MATHEMATICA
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(* first do *) Needs["Combinatorica`"] (* then *) f[n_] := Block[{d = Divisors@n, k, mx}, k = 1 + Length@d; mx = 2^Length[d]; While[k < mx && !PrimeQ[Plus @@ NthSubset[k, d]], k++ ]; If[k == mx, Length@d, 0]];
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CROSSREFS
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Sequence in context: A130003 A098581 A085420 this_sequence A113833 A157102 A121172
Adjacent sequences: A160991 A160992 A160993 this_sequence A160995 A160996 A160997
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 01 2009
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