A063796 Numbers k such that phi(sigma(k^3)) is a square.

1, 3, 10, 14, 21, 49, 66, 70, 147, 160, 224, 248, 282, 330, 403, 462, 490, 764, 803, 817, 1034, 1056, 1120, 1235, 1508, 1512, 1584, 1752, 1779, 1792, 1852, 1974, 1976, 2076, 2310, 2418, 2573, 2821, 3232, 3234, 3401, 3416, 3551, 3565, 3684, 3763, 3820, 3991

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[4000], IntegerQ[Sqrt[EulerPhi[DivisorSigma[1, #^3]]]]&] (* Harvey P. Dale, Mar 04 2015 *)

Prog

(PARI) j=[]; for(n=1, 10000, if(issquare(eulerphi(sigma(n^3))), j=concat(j, n))); j
(PARI) { n=0; for (m=1, 10^9, if(issquare(eulerphi(sigma(m^3))), write("b063796.txt", n++, " ", m); if (n==1000, break)) ) } \\ Harry J. Smith, Aug 31 2009

Crossrefs

Sequence in context: A283867 A085726 A287115 * A063221 A022409 A245524

Adjacent sequences: A063793 A063794 A063795 * A063797 A063798 A063799

Keyword

nonn

Author

Jason Earls, Aug 19 2001

Status

approved