A015729 -id:A015729

The OEIS is supported by the many generous donors to the OEIS Foundation.

Search: a015729 -id:a015729

Displaying 1-1 of 1 result found.

page 1

A238463

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

+10
1

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

(list; graph; refs; listen; history; text; internal format)

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.

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Mar 14 2014

STATUS

approved

page 1

Search completed in 0.008 seconds