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 A111386 #16 Feb 24 2024 01:12:43 %S A111386 1,3,5,15,25,75,125,375,625,1875,3125,9375,15625,46875,78125,234375, %T A111386 390625,1171875,1953125,5859375,9765625,29296875,48828125,146484375, %U A111386 244140625,732421875,1220703125,3662109375,6103515625,18310546875,30517578125 %N A111386 a(1) = 1, a(2) = 3; for n >= 3, take a(n) to be the smallest odd number not occurring earlier such that a(n-1) divides the concatenation a(n-2)a(n). %C A111386 Apparently identical to A056487! Is this a theorem? - _Klaus Brockhaus_, Jul 21 2009 %e A111386 After 75 the term is 125 since 75 divides 25125. %Y A111386 Cf. A111387. %K A111386 base,nonn %O A111386 1,2 %A A111386 _Amarnath Murthy_, Nov 11 2005 %E A111386 More terms from _R. J. Mathar_, Aug 20 2007 %E A111386 a(21)-a(31) from _Donovan Johnson_, Apr 27 2008