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 A217425 #17 Apr 08 2020 00:13:13 %S A217425 97402668820327149658203125,81209257154451887573232591061530625, %T A217425 13375863052949754169544537548117223100875, %U A217425 4587921027161765680153776379004207523600125,2478309849684200670569842256516437530517578125 %N A217425 Numbers of the form 5^r*7^s whose decimal representations are such that each digit 0-9 appears a prime number of times. %C A217425 See the formula section for more data, and other sequences in cross-reference for motivation and similar sequences. %F A217425 A217425(n) = 5^A217426(n) * 7^A217427(n). %e A217425 A217426(1)=13 and A217427(1)=20, so this sequence's first term is 5^13 * 7^20. It has two copies each of the digits 1, 3, 4, 5, 7 and 9; three each of 0's, 6's and 8's; and five 2's. %Y A217425 Cf. A217854, A217426, A217427, A217404, A217407, A217410, A217413, A217416, A217419, A217422, A217428, A217431. %K A217425 nonn,base,less %O A217425 1,1 %A A217425 _James G. Merickel_, Oct 05 2012