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 A356416 #10 Aug 28 2023 08:21:08
%S A356416 1,819,1274,19940,204323,149228720,3144583275
%N A356416 a(n) is the least start of exactly n consecutive numbers that have an equal sum of even and odd exponents in their prime factorization (A356413), or -1 if no such run of consecutive numbers exists.
%C A356416 a(8) > 6.5*10^10, if it exists.
%C A356416 a(8) <= 604912797077420. - _David A. Corneth_, Aug 06 2022
%e A356416 a(2) = 819 since 819 = 3^2 * 7 * 13 and 820 = 2^2 * 5 * 41 both have an equal sum of even and odd exponents (2) in their prime factorization, 818 and 821 have no even exponent, and 819 is the least number with this property.
%t A356416 f[p_, e_] := (-1)^e*e; q[1] = True; q[n_] := Plus @@ f @@@ FactorInteger[n] == 0; seq[len_, nmax_] := Module[{s = Table[0, {len}], v = {1}, n = 2, c = 0, m}, While[c <= len && n <= nmax, If[q[n], v = Join[v, {n}], m = Length[v]; v = {}; If[0 <= m <= len && s[[m]] == 0, c++; s[[m]] = n - m]]; n++]; s]; seq[4, 2*10^4]
%Y A356416 Cf. A356413, A356415.
%K A356416 nonn,more
%O A356416 1,2
%A A356416 _Amiram Eldar_, Aug 06 2022