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 A336673 #6 Jul 29 2020 20:39:33
%S A336673 3,49,1681,18490,23762,656914,843637,5606230,35558770,46297822,
%T A336673 59006794,114594493,132859642,138852445,157906534,289405462,299441785,
%U A336673 536671282,813736930,1175272581,1276553470,1655870629,5086602202,5429407657,6549516022,8645559934,10373399185
%N A336673 Numbers k such that A063659(k) = A063659(k+1).
%C A336673 Analogous to A001274 as A063659 is analogous to Euler's phi function (A000010).
%H A336673 E. K. Haviland, <a href="https://doi.org/10.1215/S0012-7094-44-01175-0">An analogue of Euler's phi-function</a>, Duke Math. J., Vol. 11 (1944), pp. 869-872.
%e A336673 3 is a term since A063659(3) = A063659(4) = 3.
%t A336673 f[p_, e_] := If[e == 1, p, p^e - p^(e-2)]; s[n_] := Times @@ f @@@ FactorInteger[n]; s1 = 1; seq = {}; Do[s2 = s[n]; If[s1 == s2, AppendTo[seq, n-1]]; s1 = s2, {n, 2, 10^5}]; seq
%Y A336673 Cf. A000010, A063659, A001274.
%K A336673 nonn
%O A336673 1,1
%A A336673 _Amiram Eldar_, Jul 29 2020