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

Author

Marks R. Nester

Keywords

• nonn
• easy

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

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

Crossrefs

Cf. A000481, A056470.

Programs

Mathematica

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

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]