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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A275800 n such that A275391(n) = n-2. 1
 5, 13, 17, 139, 173, 179, 467, 907, 1553, 1619, 1867, 2099, 2819, 2957, 3203, 3779, 3947, 4139, 4157, 4283, 4547, 4723, 5483, 6653, 6899, 7013, 7187, 7523, 7643, 8147, 8387, 8563, 8573, 8753, 9533, 9587, 10589, 10853, 10883, 10979, 11003, 12107, 12227, 13037, 13229, 13829, 14243, 14549, 14699, 14867, 15299, 16217, 16547, 16649, 17387, 18443, 18587, 19259 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n such that n-2 is the least k such that n divides A062727(k) = sigma(k^k). Are all terms prime? LINKS EXAMPLE 17 is in the sequence because 17 divides sigma(15^15) = 821051025385244160 but does not divide sigma(k^k) for any k < 15. MAPLE N:= 20000: S:= {\$1..N}: # to get terms <= N for kk from 1 while S <> {} do    v:= numtheory:-sigma(kk^kk);    F:= select(t -> v mod t = 0, S);    for nn in F do      B[nn]:= kk    od;    S:= S minus F; od: select(t -> B[t]=t-2, [\$1..N]); CROSSREFS Cf. A000203, A062727, A275391. Sequence in context: A294132 A125146 A051900 * A294136 A120062 A081769 Adjacent sequences:  A275797 A275798 A275799 * A275801 A275802 A275803 KEYWORD nonn AUTHOR Robert Israel, Aug 09 2016 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 November 29 21:32 EST 2021. Contains 349416 sequences. (Running on oeis4.)