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In Leibniz's Harmonic Triangle, write denominator first and then numerator of each element.
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%I #9 Jun 22 2013 16:05:38

%S 1,1,2,1,2,1,3,1,6,1,3,1,4,1,12,1,12,1,4,1,5,1,20,1,30,1,20,1,5,1,6,1,

%T 30,1,60,1,60,1,30,1,6,1,7,1,42,1,105,1,140,1,105,1,42,1,7,1,8,1,56,1,

%U 168,1,280,1,280,1,168,1,56,1,8,1,9,1,72,1,252,1,504,1,630,1,504,1,252

%N In Leibniz's Harmonic Triangle, write denominator first and then numerator of each element.

%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 1,3

%A _Mohammad K. Azarian_

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