1,2

Select a permutation of length k=floor function{n/2} from a set {1,2...,n). construct a cuboid-1 in k-th dimension. Without replacement find another permutation of same length and construct cuboid-2. Cuboid-1 can be kept within cuboid-2.

a(2n+2)= (1+2n)*a(2n) a(2n+1)= (1+2n)*a(2n) with a(2)=1,a(3)=3

a(3)=3 lists {[1][2]},{[1][3]},{[2][3]}

a(4)=15 lists {[12][34]}, {[21][34]}, {[13][24]}, {[12][35]}, {[21][35]}, {[13][25]}, {[14][35]}, {[24][35]}, {[14][25]}, {[12][45]}, {[21][45]}, {[13][45]}, {[31][45]}, {[23][45]}, {[32][45]}

Cf. A055634.

Sequence in context: A099476 A063628 A096672 this_sequence A074043 A120467 A012634

Adjacent sequences: A133224 A133225 A133226 this_sequence A133228 A133229 A133230

nonn

Srikanth K S (sriperso(AT)gmail.com), Oct 13 2007

Is this A133221 with a slightly different beginning? - njas, Oct 13 2007