cp's OEIS Frontend

A242057 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 A242057 #19 Aug 20 2014 02:34:39
%S A242057 10,16,22,26,28,34,36,40,46,50,56,64,66,70,76,82,86,92,96,100,106,112,
%T A242057 116,120,126,130,134,136,142,144,146,154,156,160,162,166,170,176,184,
%U A242057 186,190,196,202,204,206,210,214,216,222,226,232,236,244,254,256,260
%N A242057 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 A242057 An analog of A245024.
%H A242057 Jens Kruse Andersen, <a href="/A242057/b242057.txt">Table of n, a(n) for n = 1..10000</a>
%t A242057 lpf[n_]:=lpf[n]=First[First[FactorInteger[n]]];
%t A242057 lpf3[n_]:=lpf3[n]=If[#==1,1,lpf[#]]&[n/3^IntegerExponent[n,3]]
%t A242057 Select[Range[4,300,2],lpf3[#-1]<lpf3[#-3]&](* _Peter J. C. Moses_, Aug 13 2014 *)
%o A242057 (PARI) lpf3(n)=m=n/3^valuation(n, 3); if(m>1, factor(m)[1,1], 1)
%o A242057 select(n->lpf3(n-1)<lpf3(n-3), vector(200, x, 2*x)) \\ _Jens Kruse Andersen_, Aug 19 2014
%Y A242057 Cf. A245024, A243937, A020639.
%K A242057 nonn
%O A242057 1,1
%A A242057 _Vladimir Shevelev_, Aug 13 2014
%E A242057 More terms from _Peter J. C. Moses_, Aug 13 2014