A056475 Number of palindromic structures using exactly six different symbols.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 21, 21, 266, 266, 2646, 2646, 22827, 22827, 179487, 179487, 1323652, 1323652, 9321312, 9321312, 63436373, 63436373, 420693273, 420693273, 2734926558, 2734926558, 17505749898, 17505749898, 110687251039, 110687251039

Offset

1,13

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..36.

Index entries for linear recurrences with constant coefficients, signature (1,20,-20,-155,155,580,-580,-1044,1044,720,-720).

Formula

a(n) = stirling2( [(n+1)/2], 6).

G.f.: x^11/((x-1)*(2*x-1)*(2*x+1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)*(6*x^2-1)). [Colin Barker, Jul 24 2012]

Crossrefs

Cf. A000770, A056471.

Sequence in context: A246034 A220689 A056485 * A219913 A219401 A219449

Adjacent sequences: A056472 A056473 A056474 * A056476 A056477 A056478

Keyword

nonn,easy

Author

Marks R. Nester

Status

approved