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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A067224 Numbers n such that phi(5n-1) = sigma(n). 0
 5225, 20405, 181685, 210395, 302375, 302445, 524975, 1469555, 1563485, 1748855, 2791085, 3097055, 4418375, 4542065, 4735115, 5482235, 5567705, 5568615, 5683205, 5753405, 6457055, 7363013, 7531205, 8016435, 8043875, 9534185, 10511345, 10790325, 11504405 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Are there any terms not congruent to 5 in the sequence? a(22) = 7363013 is the first example. [Charles R Greathouse IV, Jan 29 2012] LINKS PROG (PARI) for(n=1, 1e8, if(sigma(n)==eulerphi(5*n-1), print1(n", "))) \\ Charles R Greathouse IV, Jan 29 2012 CROSSREFS Sequence in context: A231113 A289514 A031616 * A204139 A237408 A235296 Adjacent sequences:  A067221 A067222 A067223 * A067225 A067226 A067227 KEYWORD nonn AUTHOR Benoit Cloitre, Feb 20 2002 EXTENSIONS a(8)-a(29) from Donovan Johnson, Jan 29 2012 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 October 21 09:09 EDT 2020. Contains 337911 sequences. (Running on oeis4.)