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%I #21 May 04 2022 06:53:00
%S 5,10,13,15,17,20,25,26,29,30,34,37,39,40,41,45,50,51,52,53,58,60,61,
%T 65,68,73,74,75,78,80,82,85,87,89,90,91,97,100,101,102,104,106,109,
%U 111,113,116,117,119,120,122,123,125,130,135,136,137,143,145,146,148,149
%N Numbers whose largest prime factor is of the form 4k+1.
%C Subsequence of A009003. - _M. F. Hasler_, Feb 06 2009
%H Robert Israel, <a href="/A071821/b071821.txt">Table of n, a(n) for n = 1..10000</a>
%F Numbers k such that A006530(k) == 1 (mod 4).
%p filter:= proc(n)
%p max(numtheory:-factorset(n)) mod 4 = 1
%p end proc:
%p select(filter, [$1..200]); # _Robert Israel_, Sep 11 2020
%t Select[Range[2, 150], Mod[FactorInteger[#][[-1,1]], 4] == 1 &] (* _Amiram Eldar_, May 04 2022 *)
%o (PARI) for(n=2, 200, if((component(component(factor(n), 1), omega(n))-1)%4==0, print1(n, ", ")))
%o (PARI) for( n=2,99, vecmax(factor(n)[,1])%4==1 && print1(n",")) \\ _M. F. Hasler_, Feb 06 2009
%Y Cf. A004431, A006530, A009000, A009003, A073503, A083025.
%K easy,nonn
%O 1,1
%A _Benoit Cloitre_, Jun 07 2002
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