This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A056166 #17 Oct 11 2020 05:57:14
%S A056166 1,4,8,9,25,27,32,36,49,72,100,108,121,125,128,169,196,200,216,225,
%T A056166 243,288,289,343,361,392,441,484,500,529,675,676,800,841,864,900,961,
%U A056166 968,972,1000,1089,1125,1152,1156,1225,1323,1331,1352,1369,1372,1444
%N A056166 Numbers which are the product of distinct primes raised to prime powers.
%H A056166 Charles R Greathouse IV, <a href="/A056166/b056166.txt">Table of n, a(n) for n = 1..10000</a>
%F A056166 Sum_{n>=1} 1/a(n) = Product_{p prime} (1 + Sum_{q prime} 1/p^q) = 1.80728269690724154161... - _Amiram Eldar_, Oct 11 2020
%e A056166 200 is included because 200 = 2^3 * 5^2.
%t A056166 {1}~Join~Select[Range[1500], AllTrue[FactorInteger[#][[All, -1]], PrimeQ] &] (* _Michael De Vlieger_, Aug 20 2017 *)
%o A056166 (PARI) is(n)=#select(e->!isprime(e), factor(n)[,2])==0 \\ _Charles R Greathouse IV_, Sep 18 2015
%K A056166 nonn
%O A056166 1,2
%A A056166 _Leroy Quet_, Aug 01 2000
%E A056166 a(1) added, offset corrected by _Charles R Greathouse IV_, Sep 18 2015