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 A247415 #19 Sep 18 2018 04:20:08
%S A247415 1,4,14,51,187,695,2606,9842,37386,142693,546790,2102312,8106308,
%T A247415 31335060,121390028,471159761,1831860961,7133082300,27813493104,
%U A247415 108585087657,424396534100,1660418620528,6502345229958,25485677806201,99969379431223,392424954930562,1541494622610616,6059022365002926,23829761312067896
%N A247415 Number of friezes of type D_n.
%H A247415 B. Fontaine and P.-G. Plamondon, <a href="http://arxiv.org/abs/1409.3698">Counting friezes in type D_n</a>, arXiv:1409.3698 [math.CO], 2014.
%F A247415 a(n) = sum_{m=1..n} A000005(m)*binomial(2n-m-1,n-m).
%p A247415 a:= n -> add(numtheory:-tau(m)*binomial(2*n-m-1,n-m),m=1..n):
%p A247415 seq(a(n),n=1..100); # _Robert Israel_, Sep 17 2014
%t A247415 a[n_] := Sum[DivisorSigma[0, m] Binomial[2n-m-1, n m], {m, 1, n}]
%t A247415 Array[a, 29] (* _Jean-François Alcover_, Sep 18 2018 *)
%o A247415 (PARI) a(n) = sum(m=1,n, numdiv(m)*binomial(2*n-m-1,n-m) ); \\ _Joerg Arndt_, Sep 16 2014
%Y A247415 Cf. A000108, A247416 and A000984, the number of friezes of type A_n, B_n and C_n.
%K A247415 nonn
%O A247415 1,2
%A A247415 _Bruce Fontaine_, Sep 16 2014