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%I #14 Jan 20 2016 23:41:20
%S 1,2,1,1,2,2,1,2,1,1,0,1,2,2,1,0,1,1,1,2,0,2,1,0,0,1,1,1,2,0,0,2,2,2,
%T 1,1,0,1,2,2,1,2,2,1,0,2,1,2,1,2,1,2,1,2,0,1,1,0,2,0,2,0,1,0,2,2,1,1,
%U 1,1,0,2,1,1,1,1,2,2,2,2,1,1,2,2
%N Irregular triangle read by rows in which row n lists the base-3 digits of 2^n, n >= 0.
%C The length of row n is A020915(n) = 1 + A136409(n).
%e Triangle begins:
%e 1
%e 2
%e 1 1
%e 2 2
%e 1 2 1
%e 1 0 1 2
%e 2 1 0 1
%e 1 1 2 0 2
%e 1 0 0 1 1 1
%e 2 0 0 2 2 2
%e 1 1 0 1 2 2 1
%e 2 2 1 0 2 1 2
%e 1 2 1 2 1 2 0 1
%e 1 0 2 0 2 0 1 0 2
%e 2 1 1 1 1 0 2 1 1
%e 1 1 2 2 2 2 1 1 2 2
%t (* Replace Flatten with Grid to display the triangle: *)
%t Flatten[Table[IntegerDigits[2^n, 3], {n, 0, 15}]]
%o (PARI) for(n=0,15,for(k=1,#digits(2^n,3),print1(digits(2^n,3)[k],", "))) \\ _Derek Orr_, Dec 24 2015
%Y Cf. A000079 (powers of 2), A003137, A004642 (powers of 2 written in base 3).
%Y Cf. A265210 (base 3 digits of 2^n in reverse order).
%K nonn,tabf,base
%O 0,2
%A _L. Edson Jeffery_, Dec 04 2015
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