A238463 Numbers n such that phi(n) * sigma(n) + 1 is a perfect square.

2, 3, 5, 6, 7, 11, 13, 17, 19, 22, 23, 29, 31, 33, 37, 41, 43, 44, 47, 53, 59, 61, 67, 69, 71, 73, 76, 79, 82, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 140, 149, 151, 157, 163, 167, 173, 179, 181, 190, 191, 193, 197, 199, 211, 223, 227, 229

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[1000], IntegerQ[Sqrt[EulerPhi[#]DivisorSigma[1, #] + 1]]&]

Prog

(Magma) [n: n in [1..300] | IsSquare(EulerPhi(n) * SumOfDivisors(n) + 1)]

Crossrefs

Cf. A015727, A015728, A015729.

Sequence in context: A299157 A325327 A003174 * A352936 A340076 A340150

Adjacent sequences: A238460 A238461 A238462 * A238464 A238465 A238466

Keyword

nonn

Author

Vincenzo Librandi, Mar 14 2014

Status

approved