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 A115165 #15 Sep 08 2022 08:45:23 %S A115165 3,11,13,19,21,23,25,27,35,37,39,45,47,49,51,53,55,57,73,75,81,87,93, %T A115165 95,97,99,105,107,117,123,131,135,139,143,145,147,155,159,161,163,165, %U A115165 169,177,181,193,195,201,207,213,215,217,221,225,229,239,243,249,259,265 %N A115165 Odd numbers k such that k-1 and k+1 have the same number of distinct prime divisors. %H A115165 Amiram Eldar, <a href="/A115165/b115165.txt">Table of n, a(n) for n = 1..10000</a> %t A115165 Select[Range[1, 301, 2], PrimeNu[#-1] == PrimeNu[#+1]&] (* _Jean-François Alcover_, Oct 18 2016 *) %o A115165 (PARI) g(n) = forstep(x=3,n,2,p1=omega(x-1);p2=omega(x+1);if(p1==p2,print(x","))) %o A115165 (Magma) [k: k in [3..265 by 2]| #PrimeDivisors(k-1) eq #PrimeDivisors(k+1)]; // _Marius A. Burtea_, Feb 19 2020 %Y A115165 Subsequence of A088070. %Y A115165 Cf. A001221. %K A115165 easy,nonn %O A115165 1,1 %A A115165 _Cino Hilliard_, Mar 03 2006 %E A115165 Offset corrected by _Michel Marcus_, Oct 18 2016