This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A305930 #4 Jun 23 2018 09:18:28
%S A305930 0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,1,1,1,1,0,1,3,2,0,0,1,0,0,0,1,2,0,2,2,
%T A305930 0,4,2,3,2,2,2,2,2,1,2,2,2,1,2,3,1,2,1,2,7,6,2,5,2,4,2,2,2,1,2,4,4,3,
%U A305930 0,2,4,2,1,1,4,3,5,4,5,4,5,3,3,2,6,6,5,3,4,5,3,5,5,2,6,6,2,6,4,7
%N A305930 Number of digits '0' in 3^n (in base 10).
%F A305930 a(n) = A055641(A000244(n)).
%F A305930 a(A030700(n)) = 0; a(A305934(n)) = 1; a(A305931(n)) >= 1; a(A305933(n,k)) = n.
%e A305930 3^10 = 59049 is the smallest power of 3 having a digit 0, so a(10) = 1 is the first nonzero term.
%t A305930 Table[ Count[ IntegerDigits[3^n], 0], {n, 0, 100} ]
%t A305930 DigitCount[3^Range[0,110],10,0]
%o A305930 (PARI) apply( A305930(n)=#select(d->!d,digits(3^n)), [0..99])
%o A305930 (Haskell) a305930 = a055641 . a000244
%Y A305930 Cf. A027870 (analog for 2^k), A030700 (indices of zeros).
%Y A305930 Cf. A063555: index of first appearence of n in this sequence.
%Y A305930 Cf. A305933: table with n in row a(n).
%K A305930 nonn,base
%O A305930 0,22
%A A305930 _M. F. Hasler_, Jun 22 2018