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A268945
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Number of length-4 0..n arrays with no repeated value unequal to the previous repeated value plus one mod n+1.
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1
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10, 63, 220, 565, 1206, 2275, 3928, 6345, 9730, 14311, 20340, 28093, 37870, 49995, 64816, 82705, 104058, 129295, 158860, 193221, 232870, 278323, 330120, 388825, 455026, 529335, 612388, 704845, 807390, 920731, 1045600, 1182753, 1332970
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = n^4 + 4*n^3 + 3*n^2 + n + 1.
G.f.: x*(10 + 13*x + 5*x^2 - 5*x^3 + x^4) / (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>5.
(End)
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EXAMPLE
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Some solutions for n=9:
..9. .3. .4. .0. .0. .7. .3. .6. .2. .7. .3. .0. .7. .6. .5. .7
..2. .7. .5. .9. .0. .5. .4. .7. .8. .8. .9. .8. .0. .3. .7. .2
..6. .2. .3. .7. .8. .9. .9. .7. .3. .6. .6. .8. .8. .8. .9. .7
..2. .5. .2. .4. .9. .7. .3. .2. .5. .0. .2. .9. .7. .1. .1. .9
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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