A241692 Number of Carlitz compositions of n with exactly two descents.

2, 5, 12, 27, 53, 98, 174, 296, 486, 781, 1222, 1874, 2827, 4195, 6138, 8873, 12675, 17918, 25095, 34832, 47954, 65529, 88911, 119842, 160552, 213841, 283266, 373318, 489601, 639149, 830750, 1075292, 1386313, 1780572, 2278703, 2906137, 3694123, 4680892

Offset

6,1

Comments

No two adjacent parts of a Carlitz composition are equal.

Links

Alois P. Heinz, Table of n, a(n) for n = 6..1000

Maple

b:= proc(n, i) option remember; `if`(n=0, 1,
       convert(series(add(`if`(i=j, 0, b(n-j, j)*
      `if`(j<i, x, 1)), j=1..n), x, 3), polynom))
    end:
a:= n-> coeff(b(n, 0), x, 2):
seq(a(n), n=6..50);

Crossrefs

Column k=2 of A241701.

Sequence in context: A221950 A116716 A128812 * A078410 A096766 A362193

Adjacent sequences: A241689 A241690 A241691 * A241693 A241694 A241695

Keyword

nonn

Author

Alois P. Heinz, Apr 27 2014

Status

approved