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A242066 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. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

a(n)-3 and (a(n)-1)/3 are primes.

LINKS

Table of n, a(n) for n=3..55.

MATHEMATICA

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 *)

CROSSREFS

Cf. A242057, A242058, A242059, A242060, A242064, A242065, A242033, A242034, A242036, A242037.

Sequence in context: A059756 A242214 A242559 * A303958 A304601 A165338

Adjacent sequences:  A242063 A242064 A242065 * A242067 A242068 A242069

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Aug 13 2014

STATUS

approved

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Last modified January 21 02:59 EST 2019. Contains 319344 sequences. (Running on oeis4.)