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 A187156 Number of 3-step one space at a time bishop's tours on an n X n board summed over all starting positions. 2
 0, 0, 20, 64, 132, 224, 340, 480, 644, 832, 1044, 1280, 1540, 1824, 2132, 2464, 2820, 3200, 3604, 4032, 4484, 4960, 5460, 5984, 6532, 7104, 7700, 8320, 8964, 9632, 10324, 11040, 11780, 12544, 13332, 14144, 14980, 15840, 16724, 17632, 18564, 19520, 20500 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Row 3 of A187155. LINKS R. H. Hardin, Table of n, a(n) for n = 1..50 FORMULA Empirical: a(n) = 12*n^2 - 40*n + 32 for n>1. Conjectures from Colin Barker, Feb 28 2018: (Start) G.f.: 4*x^3*(5 + x) / (1 - x)^3. a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>4. (End) EXAMPLE Some solutions for 4 X 4: ..0..0..0..3....0..0..3..0....1..0..0..0....0..1..0..3....0..1..0..0 ..0..0..2..0....0..2..0..0....0..2..0..0....0..0..2..0....0..0..2..0 ..0..1..0..0....0..0..1..0....3..0..0..0....0..0..0..0....0..3..0..0 ..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0 CROSSREFS Cf. A187155. Sequence in context: A117432 A033577 A262486 * A246877 A074632 A225190 Adjacent sequences:  A187153 A187154 A187155 * A187157 A187158 A187159 KEYWORD nonn AUTHOR R. H. Hardin, Mar 06 2011 STATUS approved

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Last modified February 18 15:30 EST 2020. Contains 332019 sequences. (Running on oeis4.)