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 A245818 #12 Aug 18 2014 00:52:57
%S A245818 0,0,0,0,0,0,0,1,-1,0,0,0,0,2,-1,2,0,0,1,0,1,2,-1,0,-1,2,-1,1,0,-1,0,
%T A245818 2,1,2,1,-1,0,1,1,2,0,0,2,2,-1,-1,-1,0,1,-1,1,0,2,-1,-1,1,0,3,0,0,0,3,
%U A245818 -1,0,0,0,1,3,-2,0,0,0,1,2,-1,2,3,0,2,2,-4,1,-1,1,3,4,-1,0,0,-2,1,0,1,1,0,0,-1,1,1,0
%N A245818 Difference in size between rooted trees which are encoded with Matula-Goebel numbers A245822(n) and n: a(n) = A061775(A245822(n)) - A061775(n).
%H A245818 Antti Karttunen, <a href="/A245818/b245818.txt">Table of n, a(n) for n = 1..10001</a>
%F A245818 a(n) = A061775(A245822(n)) - A061775(n).
%F A245818 Other identities. For all n >= 1, the following holds:
%F A245818 a(A000040(n)) = a(n). [The result for the n-th prime is same as for n itself].
%F A245818 a(A245823(n)) = 0. [A245823 gives a (proper) subsequence of the positions of the zeros].
%o A245818 (PARI)
%o A245818 \\ Execute first the code given in A061775 and A245822.
%o A245818 A245818(n) = A061775(A245822(n)) - A061775(n);
%o A245818 for(n=1, 10001, write("b245818.txt", n, " ", A245818(n)));
%o A245818 (Scheme) (define (A245818 n) (- (A061775 (A245822 n)) (A061775 n)))
%Y A245818 Cf. A000040, A061775, A245817, A245822, A245823.
%K A245818 sign
%O A245818 1,14
%A A245818 _Antti Karttunen_, Aug 16 2014