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 A381132 #7 Mar 04 2025 23:20:54
%S A381132 0,1,2,1,3,1,4,1,2,1,5,2,6,1,2,1,7,1,8,1,2,1,9,2,3,1,2,1,10,1,11,1,2,
%T A381132 1,3,1,12,1,2,3,13,1,14,1,3,1,15,2,4,1,2,1,16,1,3,4,2,1,17,2,18,1,4,1,
%U A381132 3,1,19,1,2,1,20,1,21,1,2,1,4,1,22,3
%N A381132 If n = (p_1^e_1)*(p_2^e_2)*(p_3^e_3)*... and min(p_1^e_1,p_2^e_2,...) = p_k^e_k then a(n) = pi(p_k), a(1) = 0.
%t A381132 Table[PrimePi[Exp[MangoldtLambda[Min @@ (#[[1]]^#[[2]] & /@ FactorInteger[n])]]], {n, 80}]
%o A381132 (PARI) a(n) = if (n==1, 0, my(f=factor(n), v=vector(#f~, k, f[k,1]^f[k,2]), m=vecmin(v), i=select(x->(x==m), v, 1)); primepi(f[i[1], 1])); \\ _Michel Marcus_, Feb 19 2025
%Y A381132 Cf. A000720, A034684, A055396, A108230, A381131, A381133.
%K A381132 nonn
%O A381132 1,3
%A A381132 _Ilya Gutkovskiy_, Feb 14 2025