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A242058 Even numbers n for which lpf_3(n-1) > lpf_3(n-3), 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.

%I A242058 #19 Aug 19 2014 13:09:22
%S A242058 6,8,12,14,18,20,24,30,32,38,42,44,48,52,54,58,60,62,68,72,74,78,80,
%T A242058 84,88,90,94,98,102,104,108,110,114,118,122,124,128,132,138,140,148,
%U A242058 150,152,158,164,168,172,174,178,180,182,188,192,194,198,200,208,212
%N A242058 Even numbers n for which lpf_3(n-1) > lpf_3(n-3), 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.
%C A242058 An analog of A243937.
%H A242058 Jens Kruse Andersen, <a href="/A242058/b242058.txt">Table of n, a(n) for n = 1..10000</a>
%t A242058 lpf[n_]:=lpf[n]=First[First[FactorInteger[n]]];
%t A242058 lpf3[n_]:=lpf3[n]=If[#==1,1,lpf[#]]&[n/3^IntegerExponent[n,3]]
%t A242058 Select[Range[4,300,2],lpf3[#-1]>lpf3[#-3]&] (* _Peter J. C. Moses_, Aug 13 2014 *)
%o A242058 (PARI) lpf3(n)=m=n/3^valuation(n, 3); if(m>1, factor(m)[1,1], 1)
%o A242058 select(n->lpf3(n-1)>lpf3(n-3), vector(200, x, 2*x)) \\ _Jens Kruse Andersen_, Aug 19 2014
%Y A242058 Cf. A245024, A243937, A242057, A020639.
%K A242058 nonn
%O A242058 1,1
%A A242058 _Vladimir Shevelev_, Aug 13 2014
%E A242058 More terms from _Peter J. C. Moses_, Aug 13 2014