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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A373454 Iterate the function x <- phi(sigma(x)). The sequence has the smallest member of cycles of length 4. 8
 576, 41472, 2142720000, 3233260800 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 130767436800000 is also a term. - Jud McCranie, Jun 18 2024 LINKS Table of n, a(n) for n=1..4. EXAMPLE 576 -> 1512 -> 1280 -> 864 -> 576, so 576 (the smallest term) is in the sequence. PROG (PARI) isok(x) = my(y = eulerphi(sigma(x))); if (y > x, my(z = eulerphi(sigma(y))); if (z>x, x == eulerphi(sigma(eulerphi(sigma(z)))))); \\ Michel Marcus, Jun 07 2024 CROSSREFS Cf. A001229, A095955. A095956, A373435, A373453. Sequence in context: A223301 A168660 A268903 * A249688 A079396 A299414 Adjacent sequences: A373451 A373452 A373453 * A373455 A373456 A373457 KEYWORD nonn,more AUTHOR Jud McCranie, Jun 06 2024 STATUS approved

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

Last modified September 8 16:23 EDT 2024. Contains 375753 sequences. (Running on oeis4.)