This site is supported by donations to The OEIS Foundation.

 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!)
 A180647 Numbers n such that 5 + phi(n)^3 is prime. Phi is Euler's totient function. 0
 3, 4, 6, 13, 21, 26, 28, 35, 36, 39, 42, 43, 45, 49, 52, 56, 65, 67, 70, 72, 78, 79, 84, 86, 87, 90, 98, 104, 105, 112, 116, 127, 130, 134, 139, 140, 141, 144, 156, 158, 159, 168, 174, 177, 180, 188, 193, 199, 210, 212, 221, 236, 249, 254, 277, 278, 282, 291, 299 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The sequence appears to be infinite, but I have no proof. LINKS EXAMPLE a(5) = 21 since 5 + phi(21)^3 = 5 + 12^3 = 1733 is prime. CROSSREFS Cf. A000010. Sequence in context: A032712 A226792 A286292 * A318345 A143100 A327584 Adjacent sequences:  A180644 A180645 A180646 * A180648 A180649 A180650 KEYWORD nonn AUTHOR Carmine Suriano, Sep 14 2010 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.

Last modified December 8 09:32 EST 2019. Contains 329862 sequences. (Running on oeis4.)