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 A049190 #27 Jul 14 2025 00:19:07 %S A049190 1,3,5,59,245,2491,235253,127756731,330567489269,258479716298484155, %T A049190 36823182192123209878050549,25576412117054296344209353299113896379, %U A049190 10994511204169842163496446583221775727830456269734123253 %N A049190 Start with 1. Convert to base 2, describe it in base 2, convert to base 10. Repeat with the new result. %C A049190 a(n) is A001387(n) converted to base 10. - _Nathan Fox_, Mar 07 2018 %C A049190 "Describe" means to apply the "look-and-say" function (cf. A045918), but the "count" is again expressed in binary (and concatenated with the digit), cf. examples. - _M. F. Hasler_, Jul 12 2025 %e A049190 1 -> one 1 -> 11 -> 3; %e A049190 3 -> 11 -> two 1s -> 101 -> 5; %e A049190 5 -> 101 -> one 1, one 0, one 1 -> 111011 -> 59; %e A049190 etc. %o A049190 (PARI) A049190_first(N=13)=vector(N, i, N=if(i>1, my(d=binary(N), j=0); d=concat(d[^1]-d[^-1],-1); fromdigits(concat([concat(binary(-j+j=n), d[n]<0) | n<-[1..#d], d[n]]), 2), 1)) \\ _M. F. Hasler_, Jul 12 2025 %Y A049190 Cf. A005150, A001387. %K A049190 nonn,base %O A049190 1,2 %A A049190 _Olivier Gérard_ %E A049190 Definition and Example corrected by _Nathan Fox_, Mar 07 2018