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 A245817 #12 Aug 18 2014 00:52:48
%S A245817 0,0,0,0,0,1,0,0,-1,0,0,1,1,4,0,0,0,1,0,4,1,1,-1,0,-2,1,-1,1,0,1,0,4,
%T A245817 -2,0,1,0,1,2,-1,1,1,2,4,1,0,3,0,0,1,-2,2,-1,0,-1,-2,1,2,0,0,1,1,3,0,
%U A245817 0,0,-1,0,5,0,-2,4,2,1,3,0,0,-1,3,1,1,0,5,-1,1,-1,2,1,1,0,4,-1,0,-2,0,3,5,-2,-1,0
%N A245817 Difference in size between rooted trees which are encoded as Matula-Goebel numbers A245821(n) and n: a(n) = A061775(A245821(n)) - A061775(n).
%H A245817 Antti Karttunen, <a href="/A245817/b245817.txt">Table of n, a(n) for n = 1..10001</a>
%F A245817 a(n) = A061775(A245821(n)) - A061775(n).
%F A245817 Other identities. For all n >= 1, the following holds:
%F A245817 a(A000040(n)) = a(n). [The result for the n-th prime is same as for n itself].
%F A245817 a(A245823(n)) = 0. [A245823 gives a (proper) subsequence of the positions of the zeros].
%o A245817 (PARI)
%o A245817 \\ Execute first the code given in A061775 and A245821.
%o A245817 A245817(n) = A061775(A245821(n)) - A061775(n);
%o A245817 for(n=1, 10001, write("b245817.txt", n, " ", A245817(n)));
%o A245817 (Scheme) (define (A245817 n) (- (A061775 (A245821 n)) (A061775 n)))
%Y A245817 Cf. A000040, A061775, A245818, A245821, A245823.
%K A245817 sign
%O A245817 1,14
%A A245817 _Antti Karttunen_, Aug 16 2014