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A214944 Number of squarefree words of length 5 in an (n+1)-ary alphabet. 1
0, 30, 264, 1140, 3480, 8610, 18480, 35784, 64080, 107910, 172920, 265980, 395304, 570570, 803040, 1105680, 1493280, 1982574, 2592360, 3343620, 4259640, 5366130, 6691344, 8266200, 10124400, 12302550, 14840280, 17780364, 21168840, 25055130 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Row 5 of A214943.
LINKS
FORMULA
Empirical: a(n) = n^5 + n^4 - 2*n^3 - n^2 + n.
Conjectures from Colin Barker, Jul 22 2018: (Start)
G.f.: 6*x^2*(5 + 14*x + x^2) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.
(End)
EXAMPLE
Some solutions for n=2:
..1....2....2....0....1....0....0....0....2....1....2....2....0....2....1....2
..2....1....1....1....0....1....2....2....1....0....0....0....1....1....2....0
..0....0....2....2....2....2....1....0....0....2....1....1....0....2....0....2
..2....2....0....0....1....0....0....1....1....0....2....2....2....0....1....1
..1....1....2....2....2....1....2....0....2....1....0....1....0....1....0....0
CROSSREFS
Sequence in context: A230731 A053358 A163667 * A259455 A270852 A229427
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 30 2012
STATUS
approved

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Last modified April 22 12:55 EDT 2024. Contains 371900 sequences. (Running on oeis4.)