login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A238463 Numbers n such that phi(n) * sigma(n) + 1 is a perfect square. 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.

Sequence in context: A299157 A325327 A003174 * A166070 A053813 A116974

Adjacent sequences:  A238460 A238461 A238462 * A238464 A238465 A238466

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Mar 14 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 7 18:12 EST 2019. Contains 329847 sequences. (Running on oeis4.)