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 A084924 #14 Jan 25 2021 10:27:23 %S A084924 3,7,31,127,1279,3583,5119,6143,8191,81919,131071,524287,14680063, %T A084924 109051903,654311423,738197503,2147483647,21474836479,51539607551, %U A084924 824633720831,13743895347199,26388279066623,246290604621823 %N A084924 Let t(x) be the highest power of 2 which divides x+1. Then a(1)=3; a(n) is the least prime p for which t(p) > t(a(n-1)). %H A084924 M. F. Hasler, <a href="/A084924/b084924.txt">Table of n, a(n) for n = 1..100</a> %e A084924 a(5)=1279 because t(a(4))=7 and 1279 is the least prime with t(p)>7. %o A084924 (PARI) a=vector(50); a[1]=3;for(i=2,length(a), j=k=2^(factor(a[i-1]+1,2)[1,2]+1); while(! isprime(j-1),j+=k);a[i]=j-1); a \\ _M. F. Hasler_, Mar 15 2007 %K A084924 nonn %O A084924 1,1 %A A084924 _Shane Findley_, Jul 15 2003 %E A084924 Edited by _Don Reble_, May 08 2004 %E A084924 More terms from _M. F. Hasler_, Mar 15 2007