A071836 Numbers k such that the largest prime factor of k = prime(tau(k)).
3, 14, 21, 25, 35, 52, 114, 117, 152, 190, 266, 285, 325, 338, 343, 399, 418, 444, 464, 494, 507, 513, 627, 637, 646, 665, 666, 740, 741, 845, 969, 1036, 1045, 1183, 1184, 1235, 1272, 1463, 1573, 1590, 1615, 1628, 1665, 1729, 1850, 1859, 1924, 2116, 2120
Offset: 1
Examples
666 = 2*3^2*37, tau(666) = 12, prime(12) = 37, hence 666 is a term.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
-
Mathematica
Select[Range[2200],FactorInteger[#][[-1,1]]==Prime[DivisorSigma[0,#]]&] (* Harvey P. Dale, Aug 13 2021 *)
-
PARI
for(n=2,3000,if(component(component(factor(n),1),omega(n))==prime(numdiv(n)),print1(n,",")))
-
PARI
is(k) = if(k > 1, my(f = factor(k)); f[#f~, 1] == prime(numdiv(f)), 0); \\ Amiram Eldar, Oct 27 2024
Comments