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 A190469 #15 Mar 07 2024 01:27:56
%S A190469 14400,28224,69696,72900,78400,97344,142884,166464,193600,207936,
%T A190469 270400,304704,352836,379456,462400,484416,492804,529984,553536,
%U A190469 562500,577600,788544,842724,846400,893025,906304,968256,1052676,1065024,1132096
%N A190469 Numbers with prime factorization p^2*q^2*r^6 where p, q, and r are distinct primes.
%H A190469 T. D. Noe, <a href="/A190469/b190469.txt">Table of n, a(n) for n = 1..1000</a>
%H A190469 Will Nicholes, <a href="https://willnicholes.com/2010/06/06/list-of-prime-signatures">List of prime signatures</a>, 2010.
%H A190469 <a href="/index/Pri#prime_signature">Index to sequences related to prime signature</a>.
%F A190469 Sum_{n>=1} 1/a(n) = P(2)^2*P(6)/2 - P(2)*P(8)/2 - P(4)*P(6)/2 - P(2)*P(8) + P(10) = 0.00024535673248061231753..., where P is the prime zeta function. - _Amiram Eldar_, Mar 07 2024
%t A190469 f[n_]:=Sort[Last/@FactorInteger[n]]=={2,2,6}; Select[Range[1600000],f]
%o A190469 (PARI) list(lim)=my(v=List(),t1,t2);forprime(p=2, (lim\36)^(1/6), t1=p^6;forprime(q=2, sqrt(lim\t1), if(p==q, next);t2=t1*q^2;forprime(r=q+1, sqrt(lim\t2), if(p==r,next);listput(v,t2*r^2)))); vecsort(Vec(v)) \\ _Charles R Greathouse IV_, Jul 20 2011
%Y A190469 Cf. A190466, A190467, A190468.
%Y A190469 Cf. A085548, A085964, A085966, A085968.
%K A190469 nonn
%O A190469 1,1
%A A190469 _Vladimir Joseph Stephan Orlovsky_, May 10 2011