A056470 Number of palindromic structures using a maximum of five different symbols.

1, 1, 2, 2, 5, 5, 15, 15, 52, 52, 202, 202, 855, 855, 3845, 3845, 18002, 18002, 86472, 86472, 422005, 422005, 2079475, 2079475, 10306752, 10306752, 51263942, 51263942, 255514355, 255514355, 1275163905

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 (1,10,-10,-31,31,30,-30).

Crossrefs

Cf. A056451.

Programs

Mathematica

LinearRecurrence[{1,10,-10,-31,31,30,-30},{1,1,2,2,5,5,15},40] (* Harvey P. Dale, Dec 16 2017 *)

Formula

a(2n-1) = a(2n) = A056272(n). [R. J. Mathar, Nov 24 2010]

G.f.: -x*(19*x^6-24*x^4+9*x^2-1) / ((x-1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)). [Colin Barker, Dec 05 2012]