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A250353 Number of length 4 arrays x(i), i=1..4 with x(i) in i..i+n and no value appearing more than 2 times. 1
16, 75, 235, 581, 1221, 2287, 3935, 6345, 9721, 14291, 20307, 28045, 37805, 49911, 64711, 82577, 103905, 129115, 158651, 192981, 232597, 278015, 329775, 388441, 454601, 528867, 611875, 704285, 806781, 920071, 1044887, 1181985, 1332145 (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) = n^4 + 4*n^3 + 2*n^2 + 9*n + 1 for n>1.

Conjectures from Colin Barker, Nov 13 2018: (Start)

G.f.: x*(16 - 5*x + 20*x^2 - 4*x^3 - 4*x^4 + x^5) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>6.

(End)

EXAMPLE

Some solutions for n=6:

..2....0....2....3....3....3....2....4....4....4....1....0....2....5....5....5

..6....2....7....1....7....4....2....4....3....4....4....6....1....3....1....4

..2....4....3....5....6....7....7....6....8....2....7....2....6....6....2....5

..3....7....7....8....6....4....6....7....8....7....8....6....9....4....5....3

CROSSREFS

Row 4 of A250351.

Sequence in context: A197873 A232863 A200786 * A212690 A244835 A189949

Adjacent sequences:  A250350 A250351 A250352 * A250354 A250355 A250356

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 19 2014

STATUS

approved

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Last modified September 17 04:03 EDT 2019. Contains 327119 sequences. (Running on oeis4.)