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 A381087 #10 Feb 20 2025 08:40:50 %S A381087 2,1,6,31,64,64,331,331,814,1607,4107,5129,5129,5129,10283,12819, %T A381087 16163,16163,16163,40108,40108,40108,40108,40108,40108,80313,80313, %U A381087 80313,80313,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153,100153 %N A381087 The smallest positive integer that produces a product that contains the digit 2 when multiplied by 2 a total of n times. %C A381087 The last known distinct term is a(148) = 3130008; all subsequent terms studied also equal 3130008, and it is plausible, although unproven, that this is the last distinct value as n -> infinity. %H A381087 Scott R. Shannon, <a href="/A381087/b381087.txt">Table of n, a(n) for n = 0..500</a> %e A381087 a(2) = 6 as 6*2 = 12 and 12*2 = 24, and the two products contain the digit 2. %e A381087 a(8) = 814 as 814*2 = 1628, 1628*2 = 3256, 3256*2 = 6512, 6512*2 = 13024, 13024*2 = 26048, 26048*2 = 52096, 52096*2 = 104192, 104192*2 = 208384, and the eight products contain the digit 2. %Y A381087 Cf. A378138 (distinct values), A381183, A011532. %K A381087 nonn,base %O A381087 0,1 %A A381087 _Scott R. Shannon_, Feb 13 2025