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 A306842 #17 Jun 14 2021 02:32:43
%S A306842 1,4,6,44,10,612,14,3936,7074,22700,22,339792,26,624652,2732760,
%T A306842 6401232,34,45174204,38,220441080,309304842,325909628,46,7330314960,
%U A306842 2822796950,6760390052,27417926304,78814587656,58,548150764560,62,1352747882944,2111872688706
%N A306842 a(n) = Sum_{d|n} binomial(n,d)*binomial(n,n/d).
%H A306842 Seiichi Manyama, <a href="/A306842/b306842.txt">Table of n, a(n) for n = 1..3000</a>
%F A306842 If p is prime, a(p) = 2*p.
%t A306842 a[n_] := DivisorSum[n, Binomial[n, #] * Binomial[n, n/#] &]; Array[a, 30] (* _Amiram Eldar_, Jun 13 2021 *)
%o A306842 (PARI) {a(n) = sumdiv(n, d, binomial(n, d)*binomial(n, n/d))}
%Y A306842 Cf. A100484, A174462.
%K A306842 nonn
%O A306842 1,2
%A A306842 _Seiichi Manyama_, Mar 12 2019