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 A380625 #9 Jan 29 2025 16:35:20
%S A380625 1,2,4,21,130,1135,12448,154441,2283922,38761556,721082359,
%T A380625 14999247901,345288253975,8513996163751,228807509644648,
%U A380625 6634125686206751,203954623297226722,6705169274925371251,234777003656354137054,8632415297513570062501,335879068944350793715480
%N A380625 Number of rooted regular combinatorial maps with n edges.
%H A380625 Andrew Howroyd, <a href="/A380625/b380625.txt">Table of n, a(n) for n = 0..200</a>
%F A380625 a(n) = Sum_{d|2*n} A380622(d,2*n/d) for n > 0.
%o A380625 (PARI) a(n)={if(n==0, 1, sumdiv(2*n, d, T(d,2*n/d)))} \\ T(n,k) defined in A380622.
%Y A380625 Cf. A380622.
%K A380625 nonn
%O A380625 0,2
%A A380625 _Andrew Howroyd_, Jan 29 2025