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 A158877 #15 Oct 02 2022 13:28:48 %S A158877 1012,102,13,1031345242,103524563142,25,10467842,105263157894736842, %T A158877 37,10631694842 %N A158877 Definition of a(n): in base-n arithmetic a(n) is the smallest positive integer that is doubled when its least significant digit is moved to become the most significant digit. %C A158877 The problem has no solution in base 2, so sequence begins with the base-3 solution. The idea was suggested by a NY Times article (Sunday Magazine of Mar 29, 2009) -- in which Freeman Dyson is said to have solved the base-10 question almost instantaneously when it was posed to him -- and by the ensuing math-fun discussion. %e A158877 For n = 5, the smallest positive integer whose base-5 representation doubles when the rightmost digit is moved to become the leftmost digit is 8 = 13_5; 31_5 = 16. %e A158877 For n = 8, the smallest positive integer whose base-8 representation doubles when the rightmost digit is moved to become the leftmost digit is 21 = 25_8; 52_8 = 42. - _Robert Tanniru_, Aug 09 2022 %e A158877 For n = 13, the number can't be represented in this list as it would be 27A5 in base 13. %Y A158877 See A087502 (which is the main entry for this sequence) for these numbers written in base 10. Cf. A023094, A159774. %K A158877 nonn,base %O A158877 3,1 %A A158877 Daniel Asimov (asimov(AT)msri.org), Mar 28 2009 %E A158877 a(5) corrected by William A. Hoffman III (whoff(AT)robill.com), Apr 19 2009 %E A158877 a(8) corrected by _Robert Tanniru_, Aug 09 2022 %E A158877 a(11)-a(12) from _Robert Tanniru_, Aug 11 2022, using A087502