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 A247129 #10 Nov 20 2014 09:28:56 %S A247129 10,34,57,74,85,185,202,219,394,451,489,505,514,629,679,802,985,1057, %T A247129 1154,1285,1354,1387,1417,1717,2005,2047,2509,2594,2649,2761,2885, %U A247129 3097,3202,3277,3349,3385,3409,3459,3737,4207,4369,4377,4577 %N A247129 Semiprimes n such that phi(n) is a square. %C A247129 Freiberg & Pomerance show that this sequence is infinite and a(n) << n^2 log^2 n. %H A247129 Charles R Greathouse IV, <a href="/A247129/b247129.txt">Table of n, a(n) for n = 1..10000</a> %H A247129 Tristan Freiberg, Carl Pomerance, <a href="http://arxiv.org/abs/1410.8109">A note on square totients</a>, arXiv:1410.8109 [math.NT], 2014. %o A247129 (PARI) is(n)=issquare(eulerphi(n))&&bigomega(n)==2 %o A247129 (PARI) list(lim)=my(v=List()); forprime(p=2,sqrtint(lim\1), forprime(q=p+1, lim\p, if(issquare((p-1)*(q-1)), listput(v,p*q)))); Set(v) %Y A247129 Cf. A039770, A221285, A002496. %K A247129 nonn %O A247129 1,1 %A A247129 _Charles R Greathouse IV_, Nov 19 2014