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 A210416 #22 Apr 18 2021 02:15:11 %S A210416 2,20,1,6,21,9,22,10,15,23,19,222,220,25,27,29,32,35,200,40,201,45, %T A210416 202,47,52,203,51,59,204,64,205,69,206,74,207,79,208,84,209,89,210,94, %U A210416 211,99,212,101,108,213,114,214,120,215,118,127,132,216,131,141,217 %N A210416 List the positions of all digits 2 in the concatenation of all terms, not necessarily in order. This is the lexicographically earliest such sequence. %C A210416 See A210415 for comments, links, and code. %C A210416 See A098670 for a variant with increasing terms. - _M. F. Hasler_, Oct 08 2013 %H A210416 Danny Rorabaugh, <a href="/A210416/b210416.txt">Table of n, a(n) for n = 1..1000</a> %e A210416 The sequence starts with 2: the second digit is equal to 2. In the second position we cannot write only 2 because the first number is already 2. So we use the minimum number greater than 2 and beginning with digit 2, i.e., 20. In the third position we can write 1 because the digit in the first position is 2. And so on. %Y A210416 Cf. A098670, A210414-A210423. %K A210416 nonn,base %O A210416 1,1 %A A210416 _Paolo P. Lava_, Mar 26 2012