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A240322 Number of n X 2 0..3 arrays with no element equal to zero plus the sum of elements to its left or zero plus the sum of elements above it or one plus the sum of the elements diagonally to its northwest, modulo 4. 1
2, 5, 17, 37, 80, 213, 443, 1028, 2511, 5370, 12742, 29737, 65687, 155443, 355668, 803696, 1883007, 4285398, 9805203, 22760901, 51853646, 119272787, 275149593, 628629688, 1447871151, 3328934761, 7625189365, 17555754237, 40308328871 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-2) + 10*a(n-3) - a(n-4) - 5*a(n-5) - 15*a(n-6) + a(n-7) + 4*a(n-8) + 2*a(n-9) + 10*a(n-10) + 5*a(n-11) - 6*a(n-13) for n>14.

Empirical g.f.: x*(2 + 5*x + 13*x^2 + 7*x^3 - 2*x^4 - 16*x^5 - 15*x^6 - 3*x^7 + 2*x^8 + 11*x^9 + 13*x^10 + 3*x^11 - 3*x^12 - 4*x^13) / (1 - 2*x^2 - 10*x^3 + x^4 + 5*x^5 + 15*x^6 - x^7 - 4*x^8 - 2*x^9 - 10*x^10 - 5*x^11 + 6*x^13). - Colin Barker, Oct 27 2018

EXAMPLE

Some solutions for n=4:

..3..2....3..2....3..2....3..2....3..2....2..3....2..3....2..3....2..3....2..3

..2..1....2..1....2..3....2..1....2..1....3..2....3..0....3..0....3..0....3..0

..3..1....2..0....3..2....3..2....3..0....2..3....3..2....3..1....2..1....3..1

..2..1....2..0....2..1....3..2....3..2....2..1....3..2....3..1....2..1....2..3

CROSSREFS

Column 2 of A240327.

Sequence in context: A107630 A078523 A078324 * A276460 A002496 A127436

Adjacent sequences:  A240319 A240320 A240321 * A240323 A240324 A240325

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 03 2014

STATUS

approved

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Last modified April 11 00:03 EDT 2021. Contains 342877 sequences. (Running on oeis4.)