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A044277 Numbers n such that string 2,8 occurs in the base 9 representation of n but not of n-1. 1

%I

%S 26,107,188,234,269,350,431,512,593,674,755,836,917,963,998,1079,1160,

%T 1241,1322,1403,1484,1565,1646,1692,1727,1808,1889,1970,2051,2106,

%U 2213,2294,2375,2421,2456,2537,2618,2699,2780,2861

%N Numbers n such that string 2,8 occurs in the base 9 representation of n but not of n-1.

%H Robert Israel, <a href="/A044277/b044277.txt">Table of n, a(n) for n = 1..10000</a>

%p N:= 6000: # to get all terms <= N

%p f:= proc(n) local L,Q;

%p L:= convert(n,base,9);

%p Q:= map(`+`,[ListTools:-SearchAll(8,L[1..-2])],1);

%p if ormap(t -> (L[t]=2), Q) then 1 else 0 fi;

%p end proc:

%p V:= Vector(N,f):

%p W:= V[2..-1] - V[1..-2]:

%p select(t -> (W[t-1]=1),[$2..N]); # _Robert Israel_, Feb 24 2017

%o (PARI) has(n)=while(n>25, if(n%81==26, return(1)); n\=9); 0

%o is(n)=has(n) && !has(n-1) \\ _Charles R Greathouse IV_, Feb 24 2017

%K nonn,base

%O 1,1

%A _Clark Kimberling_

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Last modified October 3 14:56 EDT 2022. Contains 357237 sequences. (Running on oeis4.)