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Search: id:A120225
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| A120225 |
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a(n) is the minimal number k>n such that n+k and n*k+1 are primes. |
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+0
6
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| 2, 3, 4, 7, 6, 7, 10, 9, 14, 13, 18, 19, 24, 15, 16, 21, 24, 29, 22, 21, 22, 31, 30, 43, 28, 33, 34, 39, 32, 41, 36, 39, 34, 37, 66, 43, 60, 41, 50, 43, 42, 55, 46, 53, 52, 51, 50, 59, 52, 51, 56, 55, 56, 55, 58, 75, 74, 69, 68, 67, 66, 75, 74, 67, 86, 83, 70, 89, 70, 79, 102, 79
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Differs from A120224 in the first term.
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EXAMPLE
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a(3)=4 because 3+4=7 and 3*4+1=13 are prime;
a(8)=9 because 8+9=17 and 8*9+1=73 are prime,
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MATHEMATICA
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Reap[Do[Do[If[PrimeQ[{n+x, n*x+1}]=={True, True}, Sow[x]; Break[]], {x, n+1, 1000}], {n, 120}]][[2, 1]]
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CROSSREFS
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Cf. A085063, A092945, A085063, A120223, A120224.
Sequence in context: A106454 A132075 A074846 this_sequence A130685 A125595 A091202
Adjacent sequences: A120222 A120223 A120224 this_sequence A120226 A120227 A120228
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Jun 10 2006
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