cp's OEIS Frontend

A187190 Number of 3-turn rook's tours on an n X n board summed over all starting positions.

%I A187190 #15 Jul 22 2025 10:40:38
%S A187190 0,8,108,480,1400,3240,6468,11648,19440,30600,45980,66528,93288,
%T A187190 127400,170100,222720,286688,363528,454860,562400,687960,833448,
%U A187190 1000868,1192320,1410000,1656200,1933308,2243808,2590280,2975400
%N A187190 Number of 3-turn rook's tours on an n X n board summed over all starting positions.
%F A187190 Empirical: a(n) = 4*n^4 - 10*n^3 + 6*n^2.
%F A187190 Empirical G.f.: 4*x^2*(2+17*x+5*x^2)/(1-x)^5. - _Colin Barker_, Jan 22 2012
%e A187190 Some solutions for 3X3
%e A187190 ..0..0..3....0..2..3....1..0..2....0..0..3....0..3..0....0..0..0....3..2..0
%e A187190 ..0..1..2....0..1..0....0..0..0....0..0..2....0..2..1....0..2..3....0..0..0
%e A187190 ..0..0..0....0..0..0....0..0..3....0..0..1....0..0..0....0..1..0....0..1..0
%Y A187190 Row 3 of A187189.
%K A187190 nonn
%O A187190 1,2
%A A187190 _R. H. Hardin_, Mar 06 2011