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 A023390 #31 Oct 23 2014 21:07:08 %S A023390 7,10,13,16,22,31,43,61,115,223,436,1162,3250,12322,50632,300421, %T A023390 2360602,26031136,434155345,13521155011,656031631000,65253034566544, %U A023390 16513243012141246,13066154302600036600,32251566130104220405204 %N A023390 a(n+1) = a(n) written in base 7 (read in base 10); a(1) = 7. %C A023390 Floor(a(n+1)/a(n)) = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 4, 5, 7, 11, 16, 31, 48, 99, 253, 791, 2468, 10239, 61885, 512044, 4334146, 75263018, ... - _Zak Seidov_, Apr 18 2014 %C A023390 All first differences are multiples of 3. - _Zak Seidov_, Oct 21 2014 %H A023390 Vincenzo Librandi, <a href="/A023390/b023390.txt">Table of n, a(n) for n = 1..47</a> %e A023390 a(1) = 7 = 10[7], i.e., "10" in base 7, thus a(2)=10. %e A023390 a(2) = 10 = 13[7], thus a(3)=13. %t A023390 NestList[FromDigits[IntegerDigits[#, 7]] &, 7, 30] (* _Zak Seidov_, Apr 18 2014 *) %o A023390 (PARI) step(n)=fromdigits(digits(n,7),10) %o A023390 n=7;concat(n,vector(99,i,n=step(n))) \\ _Charles R Greathouse IV_, Oct 21 2014 %Y A023390 Cf. A023383. %K A023390 base,nonn %O A023390 1,1 %A A023390 _David W. Wilson_ %E A023390 Edited by _M. F. Hasler_, Oct 23 2014