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 A154893 #11 Apr 28 2018 03:37:38 %S A154893 1,2,3,5,7,11,13,16,17,19,23,29,31,36,37,41,43,47,48,53,59,61,64,67, %T A154893 71,73,79,80,81,83,89,97,100,101,103,107,109,112,113,120,127,131,137, %U A154893 139,144,149,151,157,162,163,167,168,173,176,179,181,191,193,196,197,199 %N A154893 Numbers whose number of proper divisors is not a prime number. %C A154893 Complement of A063806. %H A154893 Shawn A. Broyles, <a href="/A154893/b154893.txt">Table of n, a(n) for n = 1..10000</a> %t A154893 Select[Range[300], ! PrimeQ[DivisorSigma[0, # ] - 1] &] (* _Stefan Steinerberger_, Jan 31 2009 *) %o A154893 (PARI) isok(n) = !isprime(numdiv(n)-1); \\ _Michel Marcus_, Apr 27 2018 %Y A154893 Cf. A032741, A063806. %K A154893 easy,nonn %O A154893 1,2 %A A154893 _Omar E. Pol_, Jan 25 2009 %E A154893 More terms from _Stefan Steinerberger_, Jan 31 2009