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%I #17 Oct 11 2020 05:57:14
%S 1,4,8,9,25,27,32,36,49,72,100,108,121,125,128,169,196,200,216,225,
%T 243,288,289,343,361,392,441,484,500,529,675,676,800,841,864,900,961,
%U 968,972,1000,1089,1125,1152,1156,1225,1323,1331,1352,1369,1372,1444
%N Numbers which are the product of distinct primes raised to prime powers.
%H Charles R Greathouse IV, <a href="/A056166/b056166.txt">Table of n, a(n) for n = 1..10000</a>
%F Sum_{n>=1} 1/a(n) = Product_{p prime} (1 + Sum_{q prime} 1/p^q) = 1.80728269690724154161... - _Amiram Eldar_, Oct 11 2020
%e 200 is included because 200 = 2^3 * 5^2.
%t {1}~Join~Select[Range[1500], AllTrue[FactorInteger[#][[All, -1]], PrimeQ] &] (* _Michael De Vlieger_, Aug 20 2017 *)
%o (PARI) is(n)=#select(e->!isprime(e), factor(n)[,2])==0 \\ _Charles R Greathouse IV_, Sep 18 2015
%K nonn
%O 1,2
%A _Leroy Quet_, Aug 01 2000
%E a(1) added, offset corrected by _Charles R Greathouse IV_, Sep 18 2015
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