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 A002968 M4494 #40 Oct 21 2023 01:20:25
%S A002968 1,1,0,1,8,22,51,342,2609,16896,99114,876579,8551800,79595269,
%T A002968 764804085,8905825760
%N A002968 Number of pairings {(b(1), c(1)), (b(2), c(2)), ..., (b(n), c(n))} of the first 2n positive integers satisfying b(i) < c(i) and such that the 2n numbers c(i)+b(i) and c(i)-b(i) are all distinct.
%C A002968 Huff paper has a typographical error, a(8)=2669. - _Sean A. Irvine_, Dec 14 2014
%D A002968 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%D A002968 R. Spira, Noncomplete residue systems, Problem 71-4, SIAM Rev., 14 (1972), 173ff.
%H A002968 R. K. Guy, <a href="/A002968/a002968_1.pdf">Letter to G. B. Huff & N. J. A. Sloane, Aug 1974</a>.
%H A002968 G. B. Huff, <a href="http://matwbn.icm.edu.pl/ksiazki/aa/aa23/aa2322.pdf">On pairings of the first 2n natural numbers</a>, Acta Arithmetica, 23 (1973), 117-126.
%H A002968 D. A. Klarner, <a href="/A002968/a002968.pdf">Letter to N. J. A. Sloane, Mar 1974</a>.
%H A002968 R. Spira, <a href="/A002968/a002968_2.pdf">Noncomplete residue system Problem 71-4</a>, SIAM Rev., 14 (1972), 173-174. (Annotated scanned copy)
%Y A002968 Cf. A007631.
%K A002968 nonn,more
%O A002968 0,5
%A A002968 _N. J. A. Sloane_
%E A002968 Better definition and values of a(11)-a(15) from _Sean A. Irvine_, Dec 14 2014
%E A002968 a(0)=1 prepended by _Alois P. Heinz_, Oct 05 2018