A246475 Number of length n+3 0..4 arrays with no pair in any consecutive four terms totalling exactly 4.

172, 484, 1376, 3904, 11020, 31104, 87888, 248568, 702724, 1985932, 5612156, 15862556, 44837136, 126731180, 358188232, 1012377900, 2861418780, 8087637712, 22859103016, 64609341900, 182613147216, 516142417472, 1458837964296

Offset

1,1

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + a(n-3) + 14*a(n-4) + 3*a(n-5) + 6*a(n-6) + a(n-8) + a(n-9).

Empirical g.f.: 4*x*(43 + 35*x + 102*x^2 + 245*x^3 + 80*x^4 + 99*x^5 + 7*x^6 + 21*x^7 + 16*x^8) / (1 - 2*x - x^3 - 14*x^4 - 3*x^5 - 6*x^6 - x^8 - x^9). - Colin Barker, Nov 06 2018

Example

Some solutions for n=6:
..4....4....0....0....1....2....3....3....3....3....1....3....0....0....4....1
..4....4....0....3....1....0....4....4....2....3....1....0....0....0....2....2
..3....1....0....3....0....3....2....4....0....4....1....3....0....0....3....1
..4....2....1....3....1....3....4....4....0....4....4....0....2....3....4....1
..4....1....1....0....0....0....3....1....3....3....1....3....1....3....4....4
..4....4....2....2....2....0....4....4....0....4....1....0....0....3....4....4
..4....4....4....3....1....0....4....1....2....4....1....0....1....2....4....2
..3....4....1....3....0....3....4....2....0....2....4....2....1....3....4....3
..2....4....4....0....0....3....4....1....3....4....2....3....1....4....4....3

Crossrefs

Column 4 of A246479.

Sequence in context: A056132 A261706 A043387 * A202641 A234998 A234992

Adjacent sequences: A246472 A246473 A246474 * A246476 A246477 A246478

Keyword

nonn

Author

R. H. Hardin, Aug 27 2014

Status

approved