A056474 Number of palindromic structures using exactly five different symbols.

0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 15, 15, 140, 140, 1050, 1050, 6951, 6951, 42525, 42525, 246730, 246730, 1379400, 1379400, 7508501, 7508501, 40075035, 40075035, 210766920, 210766920, 1096190550

Offset

1,11

Comments

Permuting the symbols will not change the structure.

References

M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

Links

Table of n, a(n) for n=1..31.

Index entries for linear recurrences with constant coefficients, signature (1,14,-14,-71,71,154,-154,-120,120).

Formula

stirling2( [(n+1)/2], 5).

G.f.: -x^9/((x-1)*(2*x-1)*(2*x+1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)). [Colin Barker, Jul 24 2012]

Mathematica

Table[StirlingS2[Floor[(n+1)/2], 5], {n, 40}] (* Harvey P. Dale, Dec 18 2012 *)

Crossrefs

Cf. A000481, A056470.

Sequence in context: A036379 A070920 A056484 * A219912 A240980 A134912

Adjacent sequences: A056471 A056472 A056473 * A056475 A056476 A056477

Keyword

nonn,easy

Author

Marks R. Nester

Status

approved