0,2

Same as Pisot sequences E(1,8), L(1,8), P(1,8), T(1,8). See A008776 for definitions of Pisot sequences.

If X_1, X_2, ..., X_n is a partition of the set {1,2,...,2*n} into blocks of size 2 then, for n>=1, a(n) is equal to the number of functions f : {1,2,..., 2*n}->{1,2,3} such that for fixed y_1,y_2,...,y_n in {1,2,3} we have f(X_i)<>{y_i}, (i=1,2,...,n). - Milan R. Janjic (agnus(AT)blic.net), May 24 2007

Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 273

Tanya Khovanova, Recursive Sequences

Y. Puri and T. Ward, Arithmetic and growth of periodic orbits, J. Integer Seqs., Vol. 4 (2001), #01.2.1.

Eric Weisstein's World of Mathematics, Sierpinski Carpet

a(n) = 8^n; a(n) = 8a(n-1).

G.f.: 1/(1-8x), e.g.f.: exp(8x)

Adjacent sequences: A001015 A001016 A001017 this_sequence A001019 A001020 A001021

Sequence in context: A126629 A125498 A125908 this_sequence A097682 A050738 A046238

nonn,easy

njas