A067892 Numbers k such that tau(k)*phi(k) > prime(k) where tau(k) = A000005(k).

720, 864, 1008, 1080, 1120, 1260, 1296, 1440, 1512, 1584, 1680, 1728, 1760, 1800, 1872, 1980, 2016, 2080, 2160, 2240, 2304, 2376, 2400, 2448, 2464, 2520, 2592, 2640, 2688, 2700, 2720, 2736, 2772, 2800, 2808, 2835, 2880, 2912, 3024, 3080, 3120, 3168

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..3000 from Harvey P. Dale)

Mathematica

Select[Range[3200], EulerPhi[#]DivisorSigma[0, #]>Prime[#]&] (* Harvey P. Dale, Nov 17 2018 *)

Prog

(PARI) is(k) = numdiv(k) * eulerphi(k) > prime(k); \\ Amiram Eldar, Apr 17 2024
(PARI) lista(pmax) = {my(f, k = 0); forprime(p=1, pmax, k++; f = factor(k); if(numdiv(f) * eulerphi(f) > p, print1(k, ", "))); } \\ Amiram Eldar, Apr 17 2024

Crossrefs

Cf. A000005 (tau), A000010 (phi), A062355.

Sequence in context: A056467 A056457 A068351 * A337036 A257416 A137493

Adjacent sequences: A067889 A067890 A067891 * A067893 A067894 A067895

Keyword

easy,nonn

Author

Benoit Cloitre, Mar 02 2002

Status

approved