A363273 Irregular triangle read by rows: T(n,k) = number of unlabeled binary rooted trees with n leaves, where both children have at least k leaves, 1 <= k <= n/2.
1, 1, 2, 1, 3, 1, 6, 3, 1, 11, 5, 2, 23, 12, 6, 3, 46, 23, 12, 6, 98, 52, 29, 18, 6, 207, 109, 63, 40, 18, 451, 244, 146, 100, 54, 21, 983, 532, 325, 227, 135, 66, 2179, 1196, 745, 538, 342, 204, 66, 4850, 2671, 1688, 1237, 823, 529, 253, 10905, 6055, 3876, 2893, 1991, 1370, 782, 276
Offset: 2
Examples
Table begins: 1; 1; 2, 1; 3, 1; 6, 3, 1; 11, 5, 2; 23, 12, 6, 3; 46, 23, 12, 6; 98, 52, 29, 18, 6; 207, 109, 63, 40, 18; ...
Links
- Andrew Howroyd, Table of n, a(n) for n = 2..2501 (rows 1..100)
Programs
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PARI
T(n)={my(A=vector(n), R=vector(n)); A[1]=1; R[1]=[]; for(i=2, n, my(t=vector(i\2, j, if(2*j
Extensions
Terms a(27) and beyond from Andrew Howroyd, Jan 01 2024