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 A294672 #47 Oct 20 2023 12:34:20 %S A294672 1,1,2,4,10,26,75,226,718,2368,8083,28367 %N A294672 Number of disjoint covering systems of cardinality n, up to equivalence under shift. %C A294672 A disjoint covering system is a system of n congruences x == a_i (mod m_i) such that every integer is a solution to exactly one of the congruences. This sequence counts them up to "shift"; that is, two systems are the same if we can turn one into another by subtracting a constant from x. %H A294672 I. P. Goulden, Andrew Granville, L. Bruce Richmond, and Jeffrey Shallit, <a href="https://doi.org/10.1007/s11139-018-0030-y">Natural exact covering systems and the reversion of the Möbius series</a>, Ramanujan J. (2019) Vol. 50, 211-235. %H A294672 Břetislav Novák and Štefan Znám, <a href="http://www.jstor.org/stable/2318911">Disjoint Covering Systems</a>, The American Mathematical Monthly, Vol. 81, No. 1 (1974), 42-45. %H A294672 Wikipedia, <a href="https://en.wikipedia.org/wiki/Covering_system">Covering system</a>. %e A294672 For n = 3 there are three disjoint covering systems: %e A294672 (a) x == 0 (mod 3), x == 1 (mod 3), x == 2 (mod 3) %e A294672 (b) x == 0 (mod 2), x == 1 (mod 4), x == 3 (mod 4) %e A294672 (c) x == 1 (mod 2), x == 0 (mod 4), x == 2 (mod 4) %e A294672 but (b) and (c) are equivalent under shift. %K A294672 nonn,more %O A294672 1,3 %A A294672 _Jeffrey Shallit_, Nov 06 2017