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A242059 lpf_3(A242057(n)-1), 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. 4
1, 5, 7, 5, 1, 11, 5, 13, 5, 7, 5, 7, 5, 23, 5, 1, 5, 7, 5, 11, 5, 37, 5, 7, 5, 43, 7, 5, 47, 11, 5, 17, 5, 53, 7, 5, 13, 5, 61, 5, 7, 5, 67, 7, 5, 11, 71, 5, 13, 5, 7, 5, 1, 11, 5, 7, 5, 7, 5, 31, 5, 5, 7, 5, 103, 5, 11, 17, 5, 7, 37, 5, 113, 11, 7, 5, 13, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

An analog of A242033.

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

MATHEMATICA

lpf[n_]:=lpf[n]=First[First[FactorInteger[n]]];

lpf3[n_]:=lpf3[n]=If[#==1, 1, lpf[#]]&[n/3^IntegerExponent[n, 3]]

Map[lpf3[#-1]&, Select[Range[4, 300, 2], lpf3[#-1]<lpf3[#-3]&]](* Peter J. C. Moses, Aug 13 2014 *)

PROG

(PARI) lpf3(n)=m=n/3^valuation(n, 3); if(m>1, factor(m)[1, 1], 1)

apply(n->lpf3(n-1), select(n->lpf3(n-1)<lpf3(n-3), vector(200, x, 2*x))) \\ Jens Kruse Andersen, Aug 19 2014

CROSSREFS

Cf. A245024, A243937, A242057, A242058, A242033, A242034, A020639.

Sequence in context: A002338 A324791 A226021 * A178668 A198744 A201944

Adjacent sequences:  A242056 A242057 A242058 * A242060 A242061 A242062

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Aug 13 2014

EXTENSIONS

More terms from Peter J. C. Moses, Aug 13 2014

STATUS

approved

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Last modified September 20 21:32 EDT 2021. Contains 347591 sequences. (Running on oeis4.)