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 A061521 #9 May 21 2015 10:18:33 %S A061521 1,7,13,79,1315,79711,13151377,79711791313,1315137713157979, %T A061521 797117913137971113151315,1315137713157979131513777971179711, %U A061521 797117913137971113151315797117913131315137713151377,131513771315797913151377797117971113151377131579797971179131379711791313 %N A061521 a(0) = 1; a(n) is obtained by incrementing each digit of a(n-1) by 6. %C A061521 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. %t A061521 NestList[FromDigits[Flatten[IntegerDigits/@(IntegerDigits[#]+6)]]&,1,15] (* _Harvey P. Dale_, May 21 2015 *) %K A061521 base,nonn %O A061521 0,2 %A A061521 _Amarnath Murthy_, May 08 2001 %E A061521 More terms from Larry Reeves (larryr(AT)acm.org), May 11 2001 %E A061521 a(5)-a(12) corrected by _Harvey P. Dale_, May 21 2015