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A222294
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Least k such that a term of the Collatz (3x+1) iteration of k is divisible by prime(n).
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1
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2, 3, 3, 7, 7, 7, 7, 19, 15, 19, 27, 37, 27, 43, 27, 15, 39, 27, 39, 27, 73, 27, 27, 27, 63, 39, 27, 27, 109, 75, 127, 87, 27, 123, 99, 151, 123, 163, 27, 115, 79, 27, 127, 171, 87, 199, 187, 223, 151, 135, 27, 159, 241, 27, 171, 27, 79, 271, 277, 187, 27, 27, 307
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OFFSET
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1,1
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COMMENTS
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Note that a(n) <= prime(n). The following primes require the maximum number of iterations: 2, 3, 7, 19, 37, 43, 73, 109, 127,...
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LINKS
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MATHEMATICA
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Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Table[p = Prime[n]; k = 1; While[Select[Collatz[k], Mod[#, p] == 0 &] == {}, k++]; k, {n, 100}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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