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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069809 Numbers k such that gcd(k, phi(k)) = tau(k). 1
1, 8, 9, 18, 24, 40, 56, 84, 88, 104, 136, 152, 156, 184, 228, 232, 248, 296, 328, 344, 360, 372, 376, 424, 444, 472, 488, 516, 536, 568, 584, 632, 664, 712, 732, 776, 792, 804, 808, 824, 856, 872, 876, 904, 948, 1016, 1048, 1096, 1112, 1164, 1192, 1208 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Georg Fischer, Table of n, a(n) for n = 1..2000 (first 1835 terms by Marius A. Burtea)
MATHEMATICA
Select[Range[1300], GCD[#, EulerPhi[#]] == DivisorSigma[0, #] &] (* Jayanta Basu, Mar 21 2013 *)
PROG
(PARI) for(n=1, 1592, if(gcd(n, eulerphi(n))==numdiv(n), print1(n, ", ")))
(Magma) [n: n in [1..2000] | GCD(n, EulerPhi(n)) eq NumberOfDivisors(n) ]; // Marius A. Burtea, Dec 28 2018
CROSSREFS
Sequence in context: A050706 A159836 A230542 * A067544 A022313 A120311
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 30 2002
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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 24 17:27 EST 2024. Contains 370307 sequences. (Running on oeis4.)