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 A221527 Number of 0..n arrays of length 7 with each element differing from at least one neighbor by 2 or more. 1
 0, 16, 768, 8544, 50400, 205080, 654864, 1763328, 4184064, 9005400, 17936160, 33537504, 59505888, 101012184, 165102000, 261162240, 401458944, 601751448, 881987904, 1267087200, 1787812320, 2481740184, 3394333008, 4580116224 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Row 7 of A221524. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 1*n^7 + 1*n^6 - 29*n^5 + 109*n^4 - 204*n^3 + 202*n^2 - 80*n for n>2. Conjectures from Colin Barker, Aug 06 2018: (Start) G.f.: 8*x^2*(2 + 80*x + 356*x^2 + 332*x^3 - 97*x^4 - 22*x^5 - 28*x^6 + 8*x^7 - x^8) / (1 - x)^8. a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>10. (End) EXAMPLE Some solutions for n=6: ..4....3....4....4....0....0....3....3....3....1....4....3....3....3....4....0 ..1....5....1....6....4....5....1....0....1....3....2....6....0....0....0....6 ..1....1....6....1....5....1....6....3....0....3....1....4....6....5....0....4 ..3....5....3....0....0....6....5....0....6....5....4....2....0....3....2....6 ..6....2....2....5....5....0....1....2....3....0....0....1....2....5....6....3 ..0....0....4....2....3....6....5....3....1....4....0....6....2....0....1....2 ..4....5....6....5....0....2....3....1....4....1....6....2....5....5....3....4 CROSSREFS Cf. A221524. Sequence in context: A339202 A307923 A159375 * A129008 A134183 A042109 Adjacent sequences:  A221524 A221525 A221526 * A221528 A221529 A221530 KEYWORD nonn AUTHOR R. H. Hardin, Jan 19 2013 STATUS approved

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Last modified January 20 13:33 EST 2022. Contains 350472 sequences. (Running on oeis4.)