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A121937
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a(n) = least m >= 2 such that (n mod m) > (n+2 mod m).
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1
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3, 3, 4, 3, 3, 4, 3, 3, 5, 3, 3, 7, 3, 3, 4, 3, 3, 4, 3, 3, 11, 3, 3, 5, 3, 3, 4, 3, 3, 4, 3, 3, 5, 3, 3, 19, 3, 3, 4, 3, 3, 4, 3, 3, 23, 3, 3, 5, 3, 3, 4, 3, 3, 4, 3, 3, 29, 3, 3, 31, 3, 3, 4, 3, 3, 4, 3, 3, 5, 3, 3, 37, 3, 3, 4, 3, 3, 4, 3, 3, 41, 3, 3, 5, 3, 3, 4, 3, 3, 4, 3, 3, 5, 3, 3, 7, 3, 3, 4, 3, 3, 4
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OFFSET
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1,1
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COMMENTS
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at n = 1,4,7,... and n = 2,5,8,... a(n) = 3; also n = 3,15,27,... and n = 6,18,30,... a(n) = 4; all other terms are apparently primes. In case k=1, for all n, a(n) = least prime divisor of n+1.
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LINKS
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Table of n, a(n) for n=1..102.
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MATHEMATICA
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re=Reap[Do[Do[If[Mod[n, k]>Mod[n+2, k], Sow[k]; Break[]], {k, 2, n+2}], {n, 300}]][[2, 1]]
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CROSSREFS
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Sequence in context: A172515 A188590 A080038 * A003034 A091282 A202708
Adjacent sequences: A121934 A121935 A121936 * A121938 A121939 A121940
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov, Sep 03 2006
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STATUS
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approved
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