A218811 Hilltop maps: number of 2Xn binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..3 2Xn array

1, 15, 61, 249, 993, 3969, 15871, 63467, 253797, 1014889, 4058377, 16228793, 64896323, 259509919, 1037738269, 4149747805, 16594171517, 66357412857, 265352580967, 1061102131539, 4243176114789, 16967776245057, 67851397847697

Offset

1,2

Comments

Row 2 of A218810

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 3*a(n-1) +3*a(n-2) +3*a(n-3) +3*a(n-4) +3*a(n-5) +a(n-6) +5*a(n-7) +2*a(n-8) +2*a(n-9) +2*a(n-10) +2*a(n-11) +a(n-12) +a(n-13) -a(n-14) -a(n-15) -a(n-16) -a(n-17) -a(n-18) -a(n-19) for n>20

Example

Some solutions for n=3
..0..1..1....1..1..1....0..1..0....0..0..0....1..1..1....1..0..1....0..0..0
..1..0..0....1..1..1....1..1..0....1..1..0....0..1..1....0..1..1....1..1..1

Crossrefs

Sequence in context: A022288 A041432 A072201 * A219819 A157446 A220084

Adjacent sequences: A218808 A218809 A218810 * A218812 A218813 A218814

Keyword

nonn

Author

R. H. Hardin Nov 06 2012

Status

approved