The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.



(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A055201 Numbers k such that A005728(k) is prime. 4


%S 1,2,3,4,5,6,7,8,9,11,12,13,15,17,18,22,23,24,29,36,37,40,53,55,59,60,

%T 61,62,63,68,69,74,83,86,93,97,107,109,115,116,117,118,123,128,129,

%U 139,142,147,153,154,157,158,162,167,170,175,179,181,182,183,193,194,196

%N Numbers k such that A005728(k) is prime.

%C From a question by Leo Moser.

%D Martin Gardner, "The Last Recreations," Chapter entitled "Strong Laws of Small Primes," Copernicus, Springer-Verlag, NY, 1997, page 199.

%H Amiram Eldar, <a href="/A055201/b055201.txt">Table of n, a(n) for n = 1..10000</a>

%H Leo Moser, <a href="https://books.google.com/books?id=u6N0yfe69RcC&amp;pg=PA312">Problem P42</a>, Canadian Mathematical Bulletin, Vol. 5, No. 3 (1962), pp. 312-313.

%t s=1; Do[s = s + EulerPhi[n]; If[PrimeQ[s], Print[n]], {n, 200}]

%Y Cf. A005728.

%Y Complement of A055197.

%K easy,nonn

%O 1,2

%A _Robert G. Wilson v_, Jul 04 2000

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 April 6 18:42 EDT 2020. Contains 333286 sequences. (Running on oeis4.)