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 A098498 Number of squares on infinite half chessboard at <=n knight moves from a fixed point on the edge. 6
 1, 5, 23, 60, 110, 172, 248, 338, 442, 560, 692, 838, 998, 1172, 1360, 1562, 1778, 2008, 2252, 2510, 2782, 3068, 3368, 3682, 4010, 4352, 4708, 5078, 5462, 5860, 6272, 6698, 7138, 7592, 8060, 8542, 9038, 9548, 10072, 10610, 11162, 11728, 12308, 12902, 13510 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = 7*n^2 - n + 2, for n>3. a(n) = 3*a(n-1)-3*a(n-2)+a(n-3) for n>6. G.f.: -(2*x^6 -x^5 -6*x^4 +5*x^3 +11*x^2 +2*x +1) / (x -1)^3. - Colin Barker, Jul 14 2013 EXAMPLE 5 squares are reachable after 1 move, from these you can reach 18 new squares more, so a(1)=5 and a(2)=23. CROSSREFS See A018836 (unbounded), A098499 (diagonal halfplane), A098500 (quadrant), A098501 (octant). Sequence in context: A337750 A093622 A089137 * A159241 A179094 A176874 Adjacent sequences:  A098495 A098496 A098497 * A098499 A098500 A098501 KEYWORD nonn,easy AUTHOR Ralf Stephan, Sep 15 2004 EXTENSIONS More terms from Colin Barker, Jul 14 2013 STATUS approved

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Last modified May 9 00:09 EDT 2021. Contains 343685 sequences. (Running on oeis4.)