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 A131463 #3 Nov 11 2010 07:34:06 %S A131463 0,2,9,9,929,9,9,9,2633043,49618850,9,110361958311,2072735666087, %T A131463 1831797169511,91222349803976,1359811476184687,504939123701081904,9, %U A131463 122453792873589376894,623626925849389978443 %N A131463 Residues of 3^(2^p(n)) for Mersenne numbers with prime indices. %C A131463 M_p is prime iff 3^(M_p+1) is congruent to 9 mod M_p. Thus M_7 = 127 is prime because 3^128 mod 127 = 9 while M_11 = 2047 is composite because 3^2048 mod 2047 <> 9. %H A131463 Dennis Martin, <a href="/A131463/b131463.txt">Table of n, a(n) for n = 1..100</a> %F A131463 a(n) = 3^(2^p(n)) mod 2^p(n)-1 %e A131463 a(5) = 3^(2^11) mod 2^11-1 = 3^2048 mod 2047 = 929 %Y A131463 Cf. A095847, A001348, A131458, A131459, A131460, A131461, A131462. %K A131463 nonn %O A131463 1,2 %A A131463 Dennis Martin (dennis.martin(AT)dptechnology.com), Jul 20 2007