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 A134706 #4 Mar 30 2012 17:39:27 %S A134706 2,6,61,507,1048447,134216703,1073739775,9007199250546687, %T A134706 5192296858534827626278696515534847, %U A134706 187072209578355573530071658285452771612302071824383 %N A134706 a(n) = n-th perfect number divided by 2^n, minus 1. %F A134706 a(n)=(A000396(n)/(2^n)) - 1. %F A134706 a(n) = A134705(n)-1. - _R. J. Mathar_, Jan 30 2008 %e A134706 a(3)=61 because the 3rd perfect number is 496 and 2^3=8 and (496/8)-1=61. %Y A134706 Cf. A000396, A133028. %K A134706 nonn %O A134706 1,1 %A A134706 _Omar E. Pol_, Nov 07 2007 %E A134706 More terms from _R. J. Mathar_, Jan 30 2008