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%I #18 Oct 27 2024 09:05:41
%S 3,14,21,25,35,52,114,117,152,190,266,285,325,338,343,399,418,444,464,
%T 494,507,513,627,637,646,665,666,740,741,845,969,1036,1045,1183,1184,
%U 1235,1272,1463,1573,1590,1615,1628,1665,1729,1850,1859,1924,2116,2120
%N Numbers k such that the largest prime factor of k = prime(tau(k)).
%C Numbers k such that A006530(k) = A000040(A000005(k)).
%H Harvey P. Dale, <a href="/A071836/b071836.txt">Table of n, a(n) for n = 1..1000</a>
%e 666 = 2*3^2*37, tau(666) = 12, prime(12) = 37, hence 666 is a term.
%t Select[Range[2200],FactorInteger[#][[-1,1]]==Prime[DivisorSigma[0,#]]&] (* _Harvey P. Dale_, Aug 13 2021 *)
%o (PARI) for(n=2,3000,if(component(component(factor(n),1),omega(n))==prime(numdiv(n)),print1(n,",")))
%o (PARI) is(k) = if(k > 1, my(f = factor(k)); f[#f~, 1] == prime(numdiv(f)), 0); \\ _Amiram Eldar_, Oct 27 2024
%Y Cf. A000005, A000040, A006530, A105555.
%K easy,nonn
%O 1,1
%A _Benoit Cloitre_, Jun 08 2002