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 A055127 #10 Feb 16 2025 08:32:42 %S A055127 0,1,0,2,5,4,2,1,0,4,19,58,113,168,193,171,119,68,29,10,3,1,0,6,53, %T A055127 325,1551,6007,19533,54119,128936,266085,478223,751487,1035609, %U A055127 1254303,1336855,1254307,1035622,751526,478320,266272,129226,54484,19898,6297 %N A055127 Triangle T(n,k) of numbers of proper k-covers of an unlabeled n-set, k=1..2^n-2. %H A055127 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ProperCover.html">Proper covers</a> %e A055127 [0, 1], [0, 2, 5, 4, 2, 1], [0, 4, 19, 58, 113, 168, 193, 171, 119, 68, 29, 10, 3, 1], ...; There are 113 proper 5-covers of an unlabeled 4-set. %Y A055127 Cf. A052265, A055080, A007537. Row sums give A055152. %K A055127 nonn,tabf %O A055127 2,4 %A A055127 _Vladeta Jovovic_, Jun 14 2000