%I A014409
%S A014409 0,2,8,21,49,93,171,278,446,660,970,1347,1863,2471,3269,4188,5356,
%T A014409 6678,8316,10145,12365,14817,17743,20946,24714,28808,33566,38703,
%U A014409 44611,50955,58185,65912,74648,83946,94384,105453,117801,130853
%N A014409 Number of inequivalent ways a pair of checkers can be placed on an n 
               X n board.
%D A014409 Computed by Fred Hallden.
%F A014409 a(2n) = n/2 (2n^3 + 3n - 1); a(2n + 1) = n/2 (2n^3 + 4n^2 + 7n + 3)
%F A014409 a(n)=a(n-1)+3a(n-2)-3a(n-3)-3a(n-4)+3a(n-5)+a(n-6)-a(n-7) [From Kieren 
               MacMillan (kieren(AT)alumni.rice.edu), Nov 08 2008]
%Y A014409 Cf. A054252, A019318.
%Y A014409 Sequence in context: A141582 A000160 A034519 this_sequence A109782 A123044 
               A143229
%Y A014409 Adjacent sequences: A014406 A014407 A014408 this_sequence A014410 A014411 
               A014412
%K A014409 nonn,nice,easy
%O A014409 1,2
%A A014409 Borghard, William (bogey(AT)hostare.att.com)
%E A014409 More terms and formula from Hugo van der Sanden (hv(AT)crypt.org)