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 A370076 #15 Feb 11 2024 09:19:49
%S A370076 4,8,9,12,18,20,24,25,27,28,32,40,44,45,49,50,52,54,56,60,63,68,75,76,
%T A370076 84,88,90,92,96,98,99,104,116,117,120,121,124,125,126,128,132,135,136,
%U A370076 140,147,148,150,152,153,156,160,164,168,169,171,172,175,184,188
%N A370076 Numbers k such that A005361(k) is prime.
%C A370076 Numbers of the form m * p^q, where p and q are primes, m is squarefree, and gcd(p, m) = 1.
%C A370076 The asymptotic density of this sequence is (6/Pi^2) * Sum_{p prime} ((p/(p+1)) * Sum_{q prime} 1/p^q) = 0.2933105687... .
%C A370076 The numbers k such that A005361(k) = 1 are the squarefree numbers (A005117), whose asymptotic density is 6/Pi^2 (A059956). The complement of the union of this sequence and the squarefree numbers is the sequence of numbers k such that A005361(k) is composite, whose asymptotic density is 0.0987623... .
%H A370076 Amiram Eldar, <a href="/A370076/b370076.txt">Table of n, a(n) for n = 1..10000</a>
%t A370076 Select[Range[200], PrimeQ[Times @@ FactorInteger[#][[;;, 2]]] &]
%o A370076 (PARI) is(n) = isprime(vecprod(factor(n)[ ,2]));
%Y A370076 Cf. A005117, A005361, A053810 (subsequence), A059956.
%Y A370076 Similar sequences: A009087, A023194.
%K A370076 nonn,easy
%O A370076 1,1
%A A370076 _Amiram Eldar_, Feb 08 2024