

A056475


Number of palindromic structures using exactly six different symbols.


1



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
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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/((x1)*(2*x1)*(2*x+1)*(2*x^21)*(3*x^21)*(5*x^21)*(6*x^21)). [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



