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 A131646 #25 Nov 19 2017 13:24:30 %S A131646 0,1,2,3,4,5,6,7,8,9,18,19,20,1027,1028,1029,14745,9020076688681, %T A131646 9439828025162228377,9439829801208141318 %N A131646 Numbers that can be written from base 2 to base 18 using only the digits 0 to 9 (conjectured to be complete). %C A131646 Originally checked to 2^20356 (or 5.8*10^6127) in Nov 2008. %C A131646 It appears that 19 and 20 are the only numbers > 9 that can be written up to base 19 only using digits 0 to 9 and 20 is the only number > 9 that can be written up to base 20 only using digits 0 to 9. %C A131646 It is a plausible conjecture that there are no more terms, but this has not been proved. - _N. J. A. Sloane_, Nov 17 2017 %D A131646 B. R. Barwell, Numbers Without Letters, Journal of Recreational Mathematics, Vol. 25:3 (1993), 174-179. %H A131646 Daniel Mondot, <a href="http://archives.forumenigmes.net/index.php?showtopic=6347">Related Puzzle</a>. %t A131646 f[n_] := Total[Total@ Drop[RotateRight[DigitCount[n, #]], 10] & /@ Range[11, 18]]; Select[Range[0, 20000], f@ # == 0 &] (* _Michael De Vlieger_, Aug 29 2015 *) %o A131646 (PARI) isok(n) = if (n, for (b=11, 18, if (vecmax(digits(n,b))>9, return(0)))); 1; \\ _Michel Marcus_, Aug 30 2015 %Y A131646 Cf. A146025, A146026, A146027, A146028, A146029. %K A131646 nonn,base %O A131646 1,3 %A A131646 _Daniel Mondot_, Sep 08 2007, Nov 02 2008 %E A131646 Edited by _Charles R Greathouse IV_, Nov 01 2009 %E A131646 Reference added by _William Rex Marshall_, Oct 23 2011