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%I #32 Mar 24 2022 21:54:40
%S 210,330,390,462,510,546,570,690,714,770,798,858,870,910,930,966,1110,
%T 1122,1155,1190,1218,1230,1254,1290,1302,1326,1330,1365,1410,1430,
%U 1482,1518,1554,1590,1610,1722,1770,1785,1794,1806,1830,1870,1914,1938,1974
%N Products of four distinct primes.
%C A squarefree subsequence of A033993. Numbers like 420 = 2^2*3*5*7 with at least one prime exponent greater than 1 in the prime signature are excluded here. - _R. J. Mathar_, Apr 03 2011
%C Numbers such that omega(n) = bigomega(n) = 4. - _Michel Marcus_, Dec 15 2015
%H T. D. Noe, <a href="/A046386/b046386.txt">Table of n, a(n) for n = 1..10000</a>
%F Intersection of A014613 (product of 4 primes) and A033993 (divisible by 4 distinct primes). - _M. F. Hasler_, Mar 24 2022
%e 210 = 2*3*5*7;
%e 330 = 2*3*5*11;
%e 390 = 2*3*5*13;
%e 462 = 2*3*7*11.
%t fQ[n_] := Last /@ FactorInteger[n] == {1, 1, 1, 1}; Select[ Range[2000], fQ[ # ] &] (* _Robert G. Wilson v_, Aug 04 2005 *)
%o (PARI) is(n)=factor(n)[,2]==[1,1,1,1]~ \\ _Charles R Greathouse IV_, Sep 17 2015
%o (PARI) is(n) = omega(n)==4 && bigomega(n)==4 \\ _Hugo Pfoertner_, Dec 18 2018
%Y Cf. A001221 (omega), A001222 (bigomega), A014613 (bigomega(N) = 4) and A033993 (omega(N) = 4).
%Y Cf. A006881, A007304, this, A046387, A067885 (products of 2, 3, 4, 5 and 6 distinct primes, respectively), A046402 (4 palindromic prime factors).
%K nonn,easy
%O 1,1
%A _Patrick De Geest_, Jun 15 1998
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