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 A171995 #12 Jul 29 2024 19:22:59 %S A171995 1,625,1715,1925,2125,2875,2975,3575,3773,4165,4225,4235,4625,5125, %T A171995 5375,5425,5635,5831,5875,5915,6517,6625,7007,7225,7315,7375,7595, %U A171995 7625,7735,7889,7975,8075,8225,8281,8855,8875,9025,9425,9775,9875,10045,10075 %N A171995 Twin natural nonprimes with nonprime number of prime factors. %C A171995 Intersection of A171697 and A167175. - _R. J. Mathar_, Mar 29 2010 %e A171995 a(1)=1(without prime factors), a(2)=625(=5*5*5*5), a(3)=1715(=5*7*7*7). %o A171995 (PARI) isA171995(n)=n>0&!isprime(n)&((n%6==1&!isprime(n-2))||(n%6==5&!isprime(n+2)))&!isprime(bigomega(n)) %Y A171995 Cf. A167175, A171697. %K A171995 nonn,less %O A171995 1,2 %A A171995 _Juri-Stepan Gerasimov_, Jan 21 2010 %E A171995 Edited and extended by _Charles R Greathouse IV_, Mar 29 2010