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Index of 10^n within sequence of numbers of form 9^i*10^j.
2

%I #11 May 12 2020 12:49:34

%S 1,3,6,10,15,21,28,36,45,55,66,78,91,105,120,136,153,171,190,210,231,

%T 254,278,303,329,356,384,413,443,474,506,539,573,608,644,681,719,758,

%U 798,839,881,924,969,1015,1062,1110,1159,1209,1260,1312,1365,1419,1474,1530,1587

%N Index of 10^n within sequence of numbers of form 9^i*10^j.

%H Robert Israel, <a href="/A025747/b025747.txt">Table of n, a(n) for n = 0..2000</a>

%p N:= 10^60: # for a(0)..a(log[10](N))

%p L:= sort([seq(seq(9^i*10^j, j=0..ilog10(N/9^i)),i=0..floor(log[9](N)))]):

%p select(t -> L[t] mod 9 <> 0, [$1..nops(L)]); # _Robert Israel_, May 12 2020

%Y Cf. A022330.

%K nonn,easy

%O 0,2

%A _David W. Wilson_

%E Offset corrected by _Robert Israel_, May 12 2020