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Search: id:A067317
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| A067317 |
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n is in the sequence if 1+C(n,j) is prime for only 2 values of j (0<=j<=n), where C(n,j) is the binomial coefficient n choose j. |
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+0
2
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| 1, 3, 7, 15, 23, 31, 59, 63, 67, 81, 84, 93, 95, 127, 157, 170, 214, 239, 253, 255, 313, 470, 511, 622, 694, 1010, 1023, 1098
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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n values for which A067316(n)=2
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EXAMPLE
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The 2 values of j are 0 and n, which give the prime 2. The sequence includes all numbers 2^k-1 since C(2^k-1,j) is odd for all j.
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MATHEMATICA
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test[n_] := Module[{}, For[i=1, 2i<=n, i++, If[PrimeQ[Binomial[n, i]+1], Return[False]]]; True]; For[n=1, True, n++, If[test[n], Print[n]]]
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CROSSREFS
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Cf. A067316.
Sequence in context: A165469 A160160 A069119 this_sequence A141354 A131753 A001213
Adjacent sequences: A067314 A067315 A067316 this_sequence A067318 A067319 A067320
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KEYWORD
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more,nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jan 15 2002
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