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 A091931 #11 Mar 03 2015 00:49:59 %S A091931 0,1,1,3,3,5,1,3,7,13,15,5,9,11,15,21,27,29,3,7,9,15,19,25,33,37,39, %T A091931 43,45,49,63,3,9,11,21,23,29,35,39,45,51,53,63,65,69,71,83,95,99,101, %U A091931 105,111,113,123,1,7,13,15,21,25,27,37,51,55,57,61,75,81,91,93,97,103 %N A091931 Change the first bit to 0 in binary notation for the n-th prime. %C A091931 a(n) = A053645(A000040(n)). %H A091931 Harvey P. Dale, <a href="/A091931/b091931.txt">Table of n, a(n) for n = 1..1000</a> %F A091931 a(n) = A000040(n) - 2^(A035100(n)-1). %t A091931 FromDigits[Rest[IntegerDigits[#,2]],2]&/@Prime[Range[80]] (* _Harvey P. Dale_, Apr 20 2012 *) %o A091931 (PARI) for(n=1,72,p=prime(n);p-=2^(#binary(p)-1);print1(p,", ")) \\ _Washington Bomfim_, Jan 18 2011 %Y A091931 Cf. A091932. %K A091931 nonn,base,easy %O A091931 1,4 %A A091931 _Reinhard Zumkeller_, Feb 14 2004