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 A131462 #3 Nov 11 2010 07:34:06 %S A131462 0,3,3,3,992,3,3,3,877681,195496587,3,36787319437,1423919640546, %T A131462 3542630063906,77319946053101,6458069995222223,168313041233693968,3, %U A131462 139200566017647400916,207875641949796659481 %N A131462 Residues of 3^(2^p(n)-1) for Mersenne numbers with prime indices. %C A131462 M_p is prime iff 3 ^ M_p is congruent to 3 mod M_p. Thus M_7 = 127 is prime because 3^127 mod 127 = 3 while M_11 = 2047 is composite because 3^2047 mod 2047 <> 3. %H A131462 Dennis Martin, <a href="/A131462/b131462.txt">Table of n, a(n) for n = 1..100</a> %F A131462 a(n) = 3^(2^p(n)-1) mod 2^p(n)-1 %e A131462 a(5) = 3^(2^11-1) mod 2^11-1 = 3^2047 mod 2047 = 992 %Y A131462 Cf. A095847, A001348, A131458, A131459, A131460, A131461, A131463. %K A131462 nonn %O A131462 1,2 %A A131462 Dennis Martin (dennis.martin(AT)dptechnology.com), Jul 20 2007