A068979 Number of elements of rank n in the free lattice on three generators.

3, 6, 8, 18, 18, 56, 126, 282, 686, 1806

Offset

1,1

Comments

The rank of a lattice term is the number of occurrences of variables in that term. The rank of an element is the minimum rank of a term representing that element.

Links

Table of n, a(n) for n=1..10.

Example

a(2) = 6 because the 6 elements of rank 2 are x + y, x + z, y + z, xy, xz and yz.

Crossrefs

Sequence in context: A253855 A383295 A298860 * A101060 A278486 A038064

Adjacent sequences: A068976 A068977 A068978 * A068980 A068981 A068982

Keyword

more,nonn

Author

David Wasserman, Mar 31 2002

Status

approved