A044126 - OEIS

%I #14 Jul 17 2020 14:47:56

%S 24,60,96,132,144,168,204,240,276,312,348,360,384,420,456,492,528,564,

%T 576,600,636,672,708,744,780,792,816,852,864,924,960,996,1008,1032,

%U 1068,1104,1140,1176,1212,1224,1248,1284,1320,1356

%N Numbers n such that string 4,0 occurs in the base 6 representation of n but not of n-1.

%C All terms == 4*6^k (mod 6^(k+1)) for some k >= 1. However, not all numbers of this form are in the sequence, e.g., 888. - _Robert Israel_, Jun 13 2018

%H Robert Israel, <a href="/A044126/b044126.txt">Table of n, a(n) for n = 1..10000</a>

%p N:= 10^4: # for all terms <= N

%p filter:= proc(n) local L;

%p     L:= convert(n-1,base,6);

%p     select(t -> L[t]=0 and L[t+1]=4, [$1..nops(L)-1])=[]

%p end proc:

%p S:= convert(`union`(seq({seq(i, i=4*6^k .. N, 6^(k+1))},k=1..floor(log[6](N/4)))),list):

%p sort(select(filter, S)); # _Robert Israel_, Jun 13 2018

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,6],{4,0}]>0,1,0],{n,1500}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 17 2020 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_