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 A068406 #10 Apr 30 2016 19:47:09 %S A068406 2,3,4,5,8,9,10,11,13,22,23,28,29,34,38,41,45,46,53,55,57,58,72,76,77, %T A068406 80,81,83,85,87,88,89,91,92,93,94,100,104,106,108,112,113,117,118,121, %U A068406 122,123,124,125,128,129,131,133,143,145,147,148,152,159,160,161,162 %N A068406 Numbers n such that n and 2n+1 have the same number of prime divisors. %H A068406 Ivan Neretin, <a href="/A068406/b068406.txt">Table of n, a(n) for n = 1..10000</a> %F A068406 n such that omega(n)=omega(2n+1). %t A068406 Select[Range[162], PrimeNu[#] == PrimeNu[2 # + 1] &] (* _Ivan Neretin_, Apr 30 2016 *) %o A068406 (PARI) is(n)=omega(n)==omega(2*n+1) \\ _Charles R Greathouse IV_, Apr 30 2016 %Y A068406 Cf. A117360. %K A068406 easy,nonn %O A068406 1,1 %A A068406 _Benoit Cloitre_, Mar 09 2002