A145053 One-third of the number of n X n nonnegative integer arrays with every 3 X 3 subblock summing to 2.

15, 71, 175, 327, 987, 2079, 3603, 9831, 19947, 33951, 89787, 180615

Offset

3,1

Comments

Second differences of (a(3k), a(3k + 1), a(3k + 1)) and (a(3k + 1), a(3k + 2), a(3k + 3)) appear to be 48 * 9^(k - 1). Based on this conjecture, we would have a(15) = 306435. - David A. Corneth, Apr 15 2015

Links

Table of n, a(n) for n=3..14.

Crossrefs

Sequence in context: A000475 A253476 A308596 * A168298 A126274 A241234

Adjacent sequences: A145050 A145051 A145052 * A145054 A145055 A145056

Keyword

nonn,more

Author

R. H. Hardin, Sep 30 2008

Status

approved