A190831 Number of permutations of 4 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 2.

0, 0, 1, 1277, 1903102, 4336589521, 14956351701700, 75493034668888898

Offset

1,4

Links

Table of n, a(n) for n=1..8.

Example

Some solutions for n=4
..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1
..2....2....2....2....2....2....2....2....2....2....2....2....2....2....2....2
..3....3....3....3....3....3....3....3....3....3....3....3....3....3....3....3
..4....4....4....4....4....1....1....4....4....4....4....4....4....1....4....4
..1....1....1....2....2....4....4....1....2....1....1....2....2....4....2....2
..2....3....2....3....1....2....2....2....3....3....3....1....3....3....1....1
..4....4....4....1....4....3....3....3....1....4....2....4....1....1....3....4
..3....1....3....2....2....4....4....4....4....2....4....3....4....2....4....2
..2....2....1....4....3....1....2....1....2....3....1....1....2....4....2....3
..4....4....4....3....4....2....1....2....1....4....2....2....1....3....1....1
..1....3....2....2....1....3....3....3....4....2....4....4....3....2....4....4
..3....2....3....4....2....1....4....4....3....1....3....3....2....4....3....3
..2....1....4....1....3....4....2....1....2....3....2....2....4....1....1....2
..4....4....1....3....4....3....1....3....1....4....4....4....1....3....4....1
..3....3....3....4....1....2....4....2....3....2....3....1....3....2....2....4
..1....2....2....1....3....4....3....4....4....1....1....3....4....4....3....3

Crossrefs

Sequence in context: A282440 A211685 A210365 * A202643 A237407 A251097

Adjacent sequences: A190828 A190829 A190830 * A190832 A190833 A190834

Keyword

nonn

Author

R. H. Hardin, May 21 2011

Status

approved