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 A128303 #10 Apr 13 2025 03:20:01
%S A128303 1,3,8,12,24,29,59,66,90,97,162,172,187,224,234,335,385,412,489,531,
%T A128303 551,630,692,791,921,997,1128,1223,1256,1285,1420,1484,1518,1549,1937,
%U A128303 2146,2315,2441,2483,2556,2606,2651,2915,3124,3175,3542,3587,3645,3751,3800
%N A128303 Indices of squares (of semiprimes) in the 4-almost primes.
%H A128303 Amiram Eldar, <a href="/A128303/b128303.txt">Table of n, a(n) for n = 1..10000</a>
%F A128303 A014613(a(n)) = A074985(n) = A001358(n)^2.
%e A128303 a(5) = 24 as 196 = 14^2 = semiprime(5)^2, the 5th square in the 4-almost primes, is the 24th 4-almost prime.
%t A128303 Position[Select[Range[3*10^4], PrimeOmega[#] == 4 &], _?(IntegerQ[Sqrt[#]] &)] // Flatten (* _Amiram Eldar_, Apr 13 2025 *)
%o A128303 (PARI) list(lim) = {my(f, c); for(k = 1, lim, f = factor(k); if(bigomega(f) == 4, c++; if(vecprod(f[,2]) == 4, print1(c, ", "))));} \\ _Amiram Eldar_, Apr 13 2025
%Y A128303 Cf. A014613, A074985, A001358, A128302, A128304.
%K A128303 nonn
%O A128303 1,2
%A A128303 _Rick L. Shepherd_, Mar 04 2007