0,3

Sequence A115993 is an upper bound to this sequence. I do not know whether the two sequences differ.

F. van der Plancke n-dimensional attacking queens (with source code and executable (q3_size3_102_simple) to compute the sequence)

a(3)>=4 because we can place 4 queens on a cubic chess board, as follows: S = {(0,0,0), (1,2,0), (0,1,2), (2,0,1)}. A further queen cannot be placed at (1,0,2), for instance, because that position is attacked by (2,0,1) (and also, incidentally, by (1,2,0) and (0,1,2), but not by (0,0,0)).

Cf. A115993 (upper bound, may be equal).

Adjacent sequences: A115989 A115990 A115991 this_sequence A115993 A115994 A115995

Sequence in context: A005684 A018167 A140443 this_sequence A115993 A136424 A116732

hard,more,nonn

Frederic van der Plancke (fplancke(AT)hotmail.com), Feb 10 2006, Feb 15 2008