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 A090857 #9 Jun 06 2016 22:23:03 %S A090857 1,5,17,59,203,690,2308,7621,24913,80794,260303,834057,2660049, %T A090857 8449715,26747224,84407894,265647824,834016199,2612728134,8168761695, %U A090857 25494031748,79434416090,247130166428,767788267178,2382328079245 %N A090857 a(n) is the least positive integer such that the integer part of the arithmetic-geometric mean of a(n) and 2^n is equal to 3^n. %F A090857 floor( agm(a(n), 2^n) ) = 3^n, for n>=0. %e A090857 a(6)=2308 since floor(agm(2308,2^6))=729=3^6, but floor(agm(2307,2^6))=728. %Y A090857 Cf. A090852, A090855, A090856. %K A090857 nonn %O A090857 0,2 %A A090857 _Paul D. Hanna_, Dec 10 2003