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 A337990 #4 Oct 09 2020 05:18:07
%S A337990 1,1,6,26426,773527571233557154337704151068262296
%N A337990 Number of compositions (ordered partitions) of n^n into powers of n.
%C A337990 The next term is too large to include.
%H A337990 <a href="/index/Com#comp">Index entries for sequences related to compositions</a>
%F A337990 a(n) = [x^(n^n)] 1 / (1 - Sum_{k>=0} x^(n^k)), for n > 1.
%e A337990 a(2) = 6 because 2^2 = 4 and we have [4], [2, 2], [2, 1, 1] (3 permutations), [1, 1, 1, 1] and 1 + 1 + 3 + 1 = 6.
%t A337990 Join[{1, 1}, Table[SeriesCoefficient[1/(1 - Sum[x^(n^k), {k, 0, n}]), {x, 0, n^n}], {n, 2, 4}]]
%Y A337990 Cf. A145514, A248377.
%K A337990 nonn
%O A337990 0,3
%A A337990 _Ilya Gutkovskiy_, Oct 06 2020