%I
%S 20,22,28,33,38,46,49,50,61,68,70,76,78,86,94,103,201,204,205,217,230,
%T 256,259,260,281,327,369,391,394,395,403,422,492,550,575,583,672,675,
%U 676,740,804,815,843,1103,1165,1488,1491,1492,1543,1668
%N Positions of 3's in A181391.
%H N. J. A. Sloane, <a href="/A171953/b171953.txt">Table of n, a(n) for n = 1..143</a>
%Y Cf. A181391, A171865, A171951A171956.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Oct 29 2010
