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 A173523 #16 Mar 30 2012 17:34:04 %S A173523 1,2,3,2,3,4,3,4,5,2,3,4,3,4,5,4,5,6,3,4,5,4,5,6,5,6,7,2,3,4,3,4,5,4, %T A173523 5,6,3,4,5,4,5,6,5,6,7,4,5,6,5,6,7,6,7,8,3,4,5,4,5,6,5,6,7,4,5,6,5,6, %U A173523 7,6,7,8,5,6,7,6,7,8,7,8,9,2,3,4,3,4,5,4,5,6,3,4,5,4,5,6,5,6,7,4,5,6,5,6,7,6,7,8,3,4,5,4,5,6,5,6,7,4,5,6 %N A173523 1+A053735(n-1), where A053735 is the sum-of-digits function in base 3. %C A173523 A053735 can be obtained as 0 followed by the first 2 terms of this sequence, followed by the first 6 terms, followed by the first 18 terms, ..., followed by the first 2*3^n terms, etc. %C A173523 Similar observations are possible for: A063787 (base-2 case), and generic comments have been gathered in A173525 (base-5 case). %C A173523 Fixed point of morphism 1->123, 2->234, 3->345 etc. (start with 1). %e A173523 If written as a triangle, begins: %e A173523 1, %e A173523 2,3, %e A173523 2,3,4,3,4,5, %e A173523 2,3,4,3,4,5,4,5,6,3,4,5,4,5,6,5,6,7, %e A173523 2,3,4,3,4,5,4,5,6,3,4,5,4,5,6,5,6,7,4,5,6,5,6,7,6,7,8,... %Y A173523 Cf. A000120, A053735, A063787, A173524 - A173529. %K A173523 base,nonn %O A173523 1,2 %A A173523 _Omar E. Pol_, Feb 20 2010