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 A288542 #6 Jun 12 2017 08:59:36 %S A288542 1,0,0,0,4,29,90,188,345,825,3089,13450,54526,198846,668430,2155731, %T A288542 6963768,23265733,81163559,292726843,1073684818,3953422052, %U A288542 14517741411,53096290021,193719344526,706944953011,2586796240687,9505841335788,35102295346482 %N A288542 Number of Dyck paths of semilength n such that the minimal number of peaks over all positive levels equals three. %H A288542 Alois P. Heinz, <a href="/A288542/b288542.txt">Table of n, a(n) for n = 3..300</a> %H A288542 Wikipedia, <a href="https://en.wikipedia.org/wiki/Lattice_path#Counting_lattice_paths">Counting lattice paths</a> %e A288542 : a(7) = 4: %e A288542 : %e A288542 : /\/\/\ /\/\/\ /\/\/\ /\/\/\ %e A288542 : /\/\/\/ \ /\/\/ \/\ /\/ \/\/\ / \/\/\/\ . %Y A288542 Column k=3 of A288387. %Y A288542 Cf. A000108. %K A288542 nonn %O A288542 3,5 %A A288542 _Alois P. Heinz_, Jun 11 2017