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Even numbers in the triangle of denominators in Leibniz's Harmonic Triangle.
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%I #9 Jun 22 2013 16:05:38

%S 2,2,6,4,12,12,4,20,30,20,6,30,60,60,30,6,42,140,42,8,56,168,280,280,

%T 168,56,8,72,252,504,630,504,252,72,10,90,360,840,1260,1260,840,360,

%U 90,10,110,1320,2310,2772,2310,1320,110,12,132,660,1980,3960,5544,5544

%N Even numbers in the triangle of denominators in Leibniz's Harmonic Triangle.

%D L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 83, Problem 25.

%e 1/1; 1/2, 1/2; 1/3, 1/6, 1/3; 1/4, 1/12, 1/12, 1/4; 1/5, 1/20, 1/30, 1/20, 1/5; ...

%Y Cf. A003506.

%K tabf,nonn,easy

%O 1,1

%A _Mohammad K. Azarian_

%E More terms from _James A. Sellers_, Dec 13 1999