A268453 Number of length-n 0..4 arrays with no adjacent pair x,x+1 followed at any distance by x+1,x.

5, 25, 121, 581, 2776, 13204, 62535, 294967, 1385969, 6488635, 30273074, 140779986, 652648100, 3016745162, 13905372533, 63924885355, 293126854872, 1340883359460, 6119617278729, 27867658231717, 126637380509476, 574312506857594

Offset

1,1

Comments

Column 4 of A268457.

Links

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

Formula

Empirical: a(n) = 39*a(n-1) -693*a(n-2) +7441*a(n-3) -54053*a(n-4) +282341*a(n-5) -1103223*a(n-6) +3324255*a(n-7) -7938129*a(n-8) +15426103*a(n-9) -25019179*a(n-10) +34622055*a(n-11) -41606078*a(n-12) +43991906*a(n-13) -41304450*a(n-14) +34649044*a(n-15) -26064185*a(n-16) +17607461*a(n-17) -10675286*a(n-18) +5792770*a(n-19) -2798790*a(n-20) +1194342*a(n-21) -444872*a(n-22) +142204*a(n-23) -38049*a(n-24) +8201*a(n-25) -1336*a(n-26) +146*a(n-27) -8*a(n-28)

Example

Some solutions for n=7
..4....4....4....0....2....2....1....0....1....3....3....2....2....4....1....2
..0....0....0....3....3....0....4....4....1....3....1....1....4....3....0....1
..1....3....1....2....3....0....4....1....4....1....2....0....4....3....0....1
..4....0....1....2....3....0....2....2....4....4....2....4....2....3....0....3
..2....1....1....2....4....4....1....2....0....2....4....3....4....3....2....1
..2....3....2....1....4....4....4....2....0....1....2....2....0....0....2....3
..2....2....4....2....0....1....3....0....0....0....4....3....0....4....0....0

Crossrefs

Cf. A268457.

Sequence in context: A269463 A068539 A123871 * A343801 A218989 A078717

Adjacent sequences: A268450 A268451 A268452 * A268454 A268455 A268456

Keyword

nonn

Author

R. H. Hardin, Feb 04 2016

Status

approved