editing
approved
editing
approved
Charles R Greathouse IV, <a href="/A247129/b247129.txt">Table of n, a(n) for n = 1..10000</a>
(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)
approved
editing
reviewed
approved
proposed
reviewed
editing
proposed
allocated for Charles R Greathouse IVSemiprimes n such that phi(n) is a square.
10, 34, 57, 74, 85, 185, 202, 219, 394, 451, 489, 505, 514, 629, 679, 802, 985, 1057, 1154, 1285, 1354, 1387, 1417, 1717, 2005, 2047, 2509, 2594, 2649, 2761, 2885, 3097, 3202, 3277, 3349, 3385, 3409, 3459, 3737, 4207, 4369, 4377, 4577
1,1
Freiberg & Pomerance show that this sequence is infinite and a(n) << n^2 log^2 n.
Tristan Freiberg, Carl Pomerance, <a href="http://arxiv.org/abs/1410.8109">A note on square totients</a>, arXiv:1410.8109 [math.NT], 2014.
(PARI) is(n)=issquare(eulerphi(n))&&bigomega(n)==2
allocated
nonn
Charles R Greathouse IV, Nov 19 2014
approved
editing
allocated for Charles R Greathouse IV
recycled
allocated
editing
approved
allocated for Charles Jwo-Yue Lien
allocated
recycled
approved
editing
allocated for Charles Jwo-Yue Lien
allocated
approved