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A242066
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The smallest even k such that lpf_3(k-3) > lpf_3(k-1) >= p_n, where lpf_3(n) = lpf(n/3^t) (cf. A020639) such that 3^t (t>=0) is the maximal power of 3 which divides n.
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0
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16, 22, 34, 40, 70, 70, 70, 112, 112, 112, 130, 130, 142, 160, 184, 184, 202, 214, 310, 310, 310, 310, 310, 310, 310, 340, 340, 340, 382, 412, 412, 490, 490, 490, 490, 490, 502, 544, 544, 544, 574, 580, 634, 634, 634, 754, 754, 754, 754, 754, 754, 754, 772
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OFFSET
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3,1
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COMMENTS
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a(n)-3 and (a(n)-1)/3 are primes.
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LINKS
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MATHEMATICA
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lpf[n_]:=lpf[n]=First[First[FactorInteger[n]]]; (*least prime factor*)
lpf3[n_]:=lpf3[n]=If[#==1, 1, lpf[#]]&[n/3^IntegerExponent[n, 3]];
Table[NestWhile[#+2&, 2, !(lpf3[#-3]>lpf3[#-1]>=Prime[n])&], {n, 3, 100}] (* Peter J. C. Moses, Aug 14 2014 *)
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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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