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 A379569 #24 Jan 02 2025 12:17:10
%S A379569 0,16,94,654,4863,38243,313705,2658846,23073712,203859889,1826368510,
%T A379569 16544195786,151222451513,1392635179004,12906366376283,120260052661235
%N A379569 Number of n-digit numbers that have exactly 6 divisors.
%F A379569 Sum_{i=1..n} a(i) = Sum_{p prime} PrimePi(10^n/p^2) - PrimePi(10^(n/3)) + PrimePi(10^(n/5)). - _David Radcliffe_, Dec 29 2024
%e A379569 For n = 2 the a(2) = 16 numbers are 12, 18, 20, 28, 32, 44, 45, 50, 52, 63, 68, 75, 76, 92, 98, 99.
%o A379569 (Python)
%o A379569 from math import isqrt
%o A379569 from sympy import primerange, primepi, integer_nthroot
%o A379569 def _sum(N): return sum(primepi(N//(p * p)) for p in primerange(isqrt(N//2)+1)) - primepi(integer_nthroot(N, 3)[0]) + primepi(integer_nthroot(N, 5)[0])
%o A379569 def a379569(n): return _sum(10**n) - _sum(10**(n-1)) # _David Radcliffe_, Dec 29 2024
%Y A379569 Column k=6 of A284398. Cf. A030515 (Numbers with exactly 6 divisors).
%K A379569 nonn,more,base
%O A379569 1,2
%A A379569 _Seiichi Manyama_, Dec 26 2024
%E A379569 a(10)-a(15) from _David Radcliffe_, Dec 29 2024
%E A379569 a(16) from _David Radcliffe_, Jan 01 2025