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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A039777 Integers m such that phi(m) is equal to the sum of (the product of prime factors) and (the product of exponents) of m-1. 0
 2, 5, 21, 45, 285, 765, 27645, 196605, 41067645, 72787965, 250871805, 4295098365, 12884901885, 23307153405, 172130669565, 1766029428523005, 20978888016396285 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS No other terms below 10^24. Some large terms: 1039619980803100740810795122685, 32576974833437288924302842789885. - Max Alekseyev, Jul 28 2024 All listed terms represent solutions to phi(m) = (m+3)/2 such that (m-1)/2 is an even squarefree number. Cf. A350777. - Max Alekseyev, Jul 21 2024 a(1)=2 is the only even term below 10^100000. - Max Alekseyev, Jul 22 2024 LINKS Table of n, a(n) for n=1..17. EXAMPLE 21 is a term since 21-1 = 2^2*5^1 and (2*5)+(2*1) = 12 = phi(21). CROSSREFS Cf. A000010, A039696, A350777. Sequence in context: A230656 A266950 A328689 * A246167 A359725 A000941 Adjacent sequences: A039774 A039775 A039776 * A039778 A039779 A039780 KEYWORD nonn,more,hard AUTHOR Olivier Gérard EXTENSIONS More terms from Jud McCranie Corrected example and a(11)-a(14) from Donovan Johnson, Nov 14 2010 a(15)-a(17) from Max Alekseyev, Jul 21 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 17 23:36 EDT 2024. Contains 375991 sequences. (Running on oeis4.)