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 A273416 #13 Apr 02 2017 00:28:17
%S A273416 30,1260,1980,74256,1861860,603380175840
%N A273416 Numbers that occur 5 or more times in the triangle of denominators in Leibniz's Harmonic Triangle.
%C A273416 Of the first 6 terms the number 30 occurs 5 times, the others occur 6 times.
%C A273416 a(6) = 603380175840 is not an oblong number.
%e A273416 The number 30 appears 1 time in row 5 in the central position {5*C(4,2)}, 2 times in row 6 {6*C(5,1); 6*C(5,4)} and, trivially, 2 times in row 30 {30*C(29,0); 30*C(29,29)}.
%e A273416 The number 1260 appears 2 times in row 10 {10*C(9,4); 10*C(9,5)}, 2 times in row 36 {36*C(35,1); 36*C(35,34)} and, trivially, 2 times in row 1260 {1260*C(1259,0); 1260*C(1259,1259)}.
%Y A273416 Cf. A003506.
%K A273416 nonn,more
%O A273416 1,1
%A A273416 _Gionata Neri_, May 22 2016