A321035 Number of words of length 3n such that all letters of the quinary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting triples of identical letters into the initially empty word.

273, 15300, 564585, 17493938, 495445275, 13337746758, 348484836788, 8943435290790, 227093583305420, 5731575551864799, 144208756776131553, 3624029726937528334, 91079326041351533935, 2291027079046386970458, 57709725323735510918970, 1456179679670608615334480

Offset

5,1

Links

Alois P. Heinz, Table of n, a(n) for n = 5..773

Maple

b:= (n, k)-> `if`(n=0, 1, k/n*add(binomial(3*n, j)*(n-j)*(k-1)^j, j=0..n-1)):
a:= n-> (k-> add((-1)^i*b(n, k-i)/(i!*(k-i)!), i=0..k))(5):
seq(a(n), n=5..25);

Crossrefs

Column k=5 of A256311.

Sequence in context: A279114 A210270 A351766 * A225702 A307537 A295455

Adjacent sequences: A321032 A321033 A321034 * A321036 A321037 A321038

Keyword

nonn

Author

Alois P. Heinz, Oct 26 2018

Status

approved