A140961 Number of 3 X n {0,1}-matrices such that: (a) first and second row have a common 1, (b) second and third row have a common 1.

1, 17, 205, 2129, 20341, 184457, 1615405, 13808609, 116015461, 962575097, 7913168605, 64610052689, 524855128981, 4247421698537, 34274519697805, 275985344786369, 2218709434248901, 17815093293410777, 142915542082163005, 1145704555158361649, 9179974972732223221

Offset: 1

Author

Andi Fugard, Vladeta Jovovic, Jul 26 2008

Keywords

• easy
• nonn

Links

• Andi Fugard, Counting first-order models (with n individuals) of syllogisms.
• Index entries for linear recurrences with constant coefficients, signature (19,-118,240).

Crossrefs

Cf. A051588.

Formula

a(n) = 8^n-2*6^n+5^n.

G.f.: x*(2*x-1)/((5*x-1)*(6*x-1)*(8*x-1)). [Colin Barker, Nov 05 2012]