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A025694 Index of 2^n within sequence of numbers of form 2^i * 9^j. 1

%I

%S 1,2,3,4,6,8,10,13,16,19,23,27,31,36,41,46,52,58,64,70,77,84,91,99,

%T 107,115,124,133,142,152,162,172,183,194,205,217,229,241,253,266,279,

%U 292,306,320,334,349,364,379,395,411,427,444,461,478,496,514,532,550,569,588,607

%N Index of 2^n within sequence of numbers of form 2^i * 9^j.

%H Robert Israel, <a href="/A025694/b025694.txt">Table of n, a(n) for n = 0..10000</a>

%p f:= proc(n) local j,s,t;

%p t:= n;

%p for j from 1 do

%p s:= ilog2(9^j);

%p if s >= n then return t fi;

%p t:= t + n-1-s;

%p od

%p end proc:

%p map(f, [$1..100]); # _Robert Israel_, Dec 09 2016

%o (PARI) a(n)=my(N=1); n+1+sum(i=1, n, logint(N<<=1, 9)); \\ _Charles R Greathouse IV_, Jan 11 2018

%o (PARI) first(n)=my(s, N=1/2); vector(n+1, i, s+=logint(N<<=1, 9)+1) \\ _Charles R Greathouse IV_, Jan 11 2018

%K nonn,easy

%O 0,2

%A _David W. Wilson_

%E Offset corrected by _Charles R Greathouse IV_, Jan 11 2018

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Last modified September 19 11:26 EDT 2019. Contains 327193 sequences. (Running on oeis4.)