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 A217410 #18 Dec 22 2013 16:43:43 %S A217410 127194058437252046971768387,13246352657250963177488450589, %T A217410 1461157813024707015061910842923,12415617112031938486785960616347, %U A217410 147856680363717377959300292543841 %N A217410 Numbers of the form 3^r*7^s whose decimal representations are such that each digit 0-9 appears a prime number of times. %C A217410 See the formula section for more data, and the others in cross-reference for similar sequences and motivation. %F A217410 a(n) = 3^A217411(n) * 7^A217412(n). %e A217410 A217411(1)=37 and A217412(1)=10, so this sequence's first term is (3^37)*(7^10). It is the smallest number with exactly 3 and 7 as its prime factors to have decimal representation with each digit 0-9 counted a prime number of times. The digits 0, 2, 3, 5, 6 and 9 occur two times each; 1, 4 and 8 occur three times each; and 7 occurs five times. %Y A217410 Cf. A216854, A217411, A217412, A217404, A217407, A217410, A217416, A217419, A217422, A217425, A217428, A217431. %K A217410 nonn,base,less %O A217410 1,1 %A A217410 _James G. Merickel_, Oct 02 2012