A069809 Numbers k such that gcd(k, phi(k)) = tau(k).

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

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

Cf. A000005, A000010, A009195.

Sequence in context: A050706 A159836 A230542 * A374118 A067544 A022313

Adjacent sequences: A069806 A069807 A069808 * A069810 A069811 A069812

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 30 2002

Status

approved