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 A061517 #7 Nov 20 2020 15:35:29 %S A061517 0,4,8,12,56,910,1354,5798,9111312,13555756,5799911910, %T A061517 911131313551354,1355575757995798,579991191191113139111312, %U A061517 9111313135513551355575713555756,135557575799579957999119115799911910 %N A061517 a(0) = 0; a(n) is obtained by incrementing each digit of a(n-1) by 4. %C A061517 In A061511-A061522, A061746-A061750 when the incremented digit exceeds 9 it is written as a 2-digit string. So 9+1 becomes the 2-digit string 10, etc. %H A061517 Harvey P. Dale, <a href="/A061517/b061517.txt">Table of n, a(n) for n = 0..27</a> %t A061517 NestList[FromDigits[Flatten[IntegerDigits/@(IntegerDigits[#]+4)]]&,0,20] (* _Harvey P. Dale_, Nov 20 2020 *) %K A061517 base,nonn %O A061517 0,2 %A A061517 _Amarnath Murthy_, May 08 2001 %E A061517 More terms from Larry Reeves (larryr(AT)acm.org), May 11 2001