A272643 Irregular triangle read by rows, enumerating permutations of "specification (321^{n-5})".

1, 6, 3, 1, 17, 33, 9, 1, 40, 184, 168, 27, 1, 87, 792, 1592, 807, 81

Offset

5,2

Comments

Related to Simon Newcomb's problem.

It would be nice to have a more precise definition. See Kaplansky-Riordan, Section 7.

Links

Table of n, a(n) for n=5..22.

Irving Kaplansky and John Riordan, The problem of the rooks and its applications, Duke Mathematical Journal 13.2 (1946): 259-268.

Irving Kaplansky and John Riordan, The problem of the rooks and its applications, in Combinatorics, Duke Mathematical Journal, 13.2 (1946): 259-268. [Annotated scanned copy]

Example

The triangle starts at row n=5:
1, 6, 3,
1, 17, 33, 9,
1, 40, 184, 168, 27,
1, 87, 792, 1592, 807, 81,
...

Crossrefs

Sequence in context: A192741 A240264 A119743 * A243424 A182227 A108451

Adjacent sequences: A272640 A272641 A272642 * A272644 A272645 A272646

Keyword

nonn,tabf,more

Author

N. J. A. Sloane, May 07 2016

Status

approved