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 A074852 #20 May 13 2013 01:54:06 %S A074852 9,25,27,81,125,6561,24389,59049,161051,357911,571787,1442897,4782969, %T A074852 5177717,14348907,18191447,30080231,73560059,80062991,118370771, %U A074852 127263527,131872229,318611987,344472101,440711081,461889917,590589719 %N A074852 Composite n such that n and n+2 are prime powers. %H A074852 Charles R Greathouse IV, <a href="/A074852/b074852.txt">Table of n, a(n) for n = 1..10000</a> %o A074852 (PARI) list(lim)=my(v=List(),t);lim+=.5;for(e=2,log(lim)\log(3), forprime(p=3, lim^(1/e),ispower(t=p^e+2,,&t); if(isprime(t), listput(v,p^e)))); vecsort(Vec(v)) %o A074852 \\ _Charles R Greathouse IV_, Apr 30 2012 %o A074852 (PARI) list(lim)=my(v=List());if(lim>=25,listput(v,25));lim+=.5;for(e=2, log(lim)\log(3), forprime(p=3, lim^(1/e),if(isprime(p^e+2), listput(v, p^e)))); vecsort(Vec(v)) %o A074852 /* This second program assumes A076427(2) = 1 but is about a hundred times faster. I proved that it is correct up to 10^20 without this assumption. */ %o A074852 \\ _Charles R Greathouse IV_, Apr 30 2012 %Y A074852 Cf. A006549, A053702. %K A074852 nonn %O A074852 1,1 %A A074852 _Benoit Cloitre_, Sep 10 2002 %E A074852 More terms from _Sascha Kurz_, Jan 30 2003