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 A157966 #15 Apr 25 2024 23:59:45 %S A157966 0,1,1,1,3,3,5,5,7,9,9,11,13,13,15,17,19,19,21,23,23,25,27,29,31,33, %T A157966 33,35,35,37,41,43,45,45,49,49,51,53,55,57,59,59,63,63,65,65,69,73,75, %U A157966 75,77,79,79,83,85,87,89,89,91,93,93,97,101,103,103,105,109,111,115,115,117 %N A157966 Number of 3's in A157733(n). %C A157966 Odd numbers missing in the sequence: 39, 47, 61, 67, 71, 81, 95, 99, 107, 113, 137, 141 etc. %C A157966 The numbers above are essentially 2*A060461(n) - 1. - _Mikhail Kurkov_, Dec 18 2021 %F A157966 a(n) = floor((prime(n)-2)/3) for n != 2. - _Kevin Ryde_, Apr 25 2024 %o A157966 (PARI) a(n) = if(n==2,1, (prime(n)-2)\3); \\ _Kevin Ryde_, Apr 25 2024 %Y A157966 Cf. A157733, A060461. %K A157966 nonn,easy %O A157966 0,5 %A A157966 _Paul Curtz_, Mar 10 2009 %E A157966 Edited and extended by _R. J. Mathar_, Mar 15 2009