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Triangle read by rows: T(n,k) = number of normal planar lambda terms of size n with k free variables (n >= 1, 1 <= k <= n).
1

%I #8 Apr 23 2015 12:32:29

%S 1,2,1,9,6,2,54,40,20,5,378,295,175,70,14,2916,2346,1526,756,252,42,

%T 24057,19739,13587,7602,3234,924,132,208494,173426,123978,74964,36828,

%U 13728,3432,429

%N Triangle read by rows: T(n,k) = number of normal planar lambda terms of size n with k free variables (n >= 1, 1 <= k <= n).

%H Noam Zeilberger, Alain Giorgetti, <a href="http://arxiv.org/abs/1408.5028">A correspondence between rooted planar maps and normal planar lambda terms</a>, arXiv:1408.5028 [cs.LO], 2014.

%e Triangle begins:

%e 1

%e 2,1

%e 9,6,2

%e 54,40,20,5

%e 378,295,175,70,14

%e 2916,2346,1526,756,252,42

%e 24057,19739,13587,7602,3234,924,132,

%e 208494,173426,123978,74964,36828,13728,3432,429

%e ...

%Y Cf. A000108, A000984, A000168, A246322.

%K nonn,tabl

%O 1,2

%A _N. J. A. Sloane_, Aug 28 2014