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Triangle read by rows: T(n,k) = number of neutral planar lambda terms of size n with k free variables (n >= 0, 1 <= k <= n+1).
1

%I #15 Feb 13 2024 09:56:57

%S 1,1,1,3,4,2,14,20,15,5,83,120,105,56,14,570,820,770,504,210,42,4318,

%T 6152,5985,4368,2310,792,132,35068,49448,49014,38136,23100,10296,3003,

%U 429

%N Triangle read by rows: T(n,k) = number of neutral planar lambda terms of size n with k free variables (n >= 0, 1 <= k <= n+1).

%H Noam Zeilberger and 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 1,1

%e 3,4,2

%e 14,20,15,5

%e 83,120,105,56,14,

%e 570,820,770,504,210,42

%e 4318,6152,5985,4368,2310,792,132

%e 35068,49448,49014,38136,23100,10296,3003,429

%e ...

%Y Cf. A000108, A001791, A220910, A246323.

%K nonn,tabl,more

%O 0,4

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