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 A057887 #3 Mar 30 2012 17:37:51 %S A057887 0,0,0,1,1,2,3,4,7,8,13,13,22,22,33,33,50,45,70,65,92,87,125,111,160, %T A057887 145,196,184,252,215,308,278,359,330,440,385,525,464,593,546,715,606, %U A057887 825,735,905,832,1078,926,1219,1065,1328,1223,1547,1310,1715,1529,1855 %N A057887 Number of 4-tuples of integers with GCD=1 and giving the lengths of sides of a nondegenerate quadrilateral with perimeter n. %F A057887 Moebius transform of A057886. %e A057887 There are five quadrilaterals with perimeter 8, with sides (1,1,3,3), (1,2,2,3), (1,2,3,2), (1,3,1,3) and (2,2,2,2). (2,2,2,2) is omitted since it has GCD=2, so a(8)=4. %Y A057887 Cf. A051493. %K A057887 nonn %O A057887 1,6 %A A057887 _John W. Layman_, Sep 19 2000