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A218283
Hilltop maps: number of n X 3 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or vertical neighbor in a random 0..4 n X 3 array.
1
7, 63, 511, 4091, 32739, 261905, 2095233, 16761837, 134094563, 1072755573, 8582037499, 68656243311, 549249492763, 4393992312383, 35151909460619, 281215043377605, 2249718488563135, 17997733040855701, 143981745385748627
OFFSET
1,1
COMMENTS
Column 3 of A218288.
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) +7*a(n-2) +7*a(n-3) +7*a(n-4) +7*a(n-5) +6*a(n-6) +12*a(n-7) +10*a(n-8) +48*a(n-9) +9*a(n-10) +9*a(n-11) +9*a(n-12) +9*a(n-13) +9*a(n-14) +5*a(n-15) +13*a(n-16) +11*a(n-17) -52*a(n-18) -64*a(n-19) -64*a(n-20) -64*a(n-21) -63*a(n-22) -59*a(n-23) -48*a(n-24) -38*a(n-25) +13*a(n-26) +41*a(n-27) +48*a(n-28) +48*a(n-29) +48*a(n-30) +46*a(n-31) +33*a(n-32) +15*a(n-33) +5*a(n-34) -5*a(n-35) -7*a(n-36) -7*a(n-37) -7*a(n-38) -7*a(n-39) -6*a(n-40) -2*a(n-41) +2*a(n-42) -a(n-44) -a(n-45) -a(n-46) -a(n-47) -a(n-48) -a(n-49).
EXAMPLE
Some solutions for n=3
..0..0..1....0..1..0....1..1..1....1..0..0....0..1..0....0..1..1....0..1..1
..0..1..0....0..1..1....0..0..1....0..1..0....0..1..1....1..1..0....0..1..1
..0..0..0....1..0..0....1..0..1....0..0..0....0..1..1....1..0..0....0..0..0
CROSSREFS
Cf. A218288.
Sequence in context: A218367 A218314 A218633 * A218237 A024088 A291034
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 25 2012
STATUS
approved