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 A062103 Number of paths by which an unpromoted knight (keima) of Shogi can move to various squares on infinite board, if it starts from its origin square, the second leftmost square of the back rank. 4
 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 14 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,20 COMMENTS Table formatted as a square array shows the top-left corner of the infinite board. This is an aerated and sligthly skewed variant of Catalan's triangle A009766. LINKS Hans L. Bodlaender, The Chess Variant Pages Fairbairn, Leggett et al., Information about Shogi (Japanese chess) MAPLE [seq(ShoogiKnightSeq(j), j=1..120)]; ShoogiKnightSeq := n -> ShoogiKnightTriangle(trinv(n-1)-1, (n-((trinv(n-1)*(trinv(n-1)-1))/2))-1); ShoogiKnightTriangle := proc(r, m) option remember; if(m < 0) then RETURN(0); fi; if(r < 0) then RETURN(0); fi; if(m > r) then RETURN(0); fi; if((1 = r) and (0 = m)) then RETURN(1); fi; RETURN(ShoogiKnightTriangle(r-3, m-2) + ShoogiKnightTriangle(r-1, m-2)); end; MATHEMATICA trinv[n_] := Floor[(1 + Sqrt[8 n + 1])/2]; ShoogiKnightSeq[n_] := ShoogiKnightTriangle[trinv[n - 1] - 1, (n - ((trinv[n - 1]*(trinv[n - 1] - 1))/2)) - 1]; ShoogiKnightTriangle[r_, m_] := ShoogiKnightTriangle[r, m] = Which[m < 0, 0, r < 0, 0, m > r, 0, r == 1 && m == 0, 1, True, ShoogiKnightTriangle[r - 3, m - 2] + ShoogiKnightTriangle[r - 1, m - 2]]; Array[ShoogiKnightSeq, 120] (* Jean-François Alcover, Mar 06 2016, adapted from Maple *) CROSSREFS A009766, A049604, A062104, trinv given at A054425. Sequence in context: A181009 A270599 A091398 * A112314 A280799 A104261 Adjacent sequences:  A062100 A062101 A062102 * A062104 A062105 A062106 KEYWORD nonn,tabl AUTHOR Antti Karttunen, May 30 2001 STATUS approved

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Last modified December 14 04:53 EST 2018. Contains 318090 sequences. (Running on oeis4.)