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Search: id:A018836
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| A018836 |
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Number of squares on infinite chess-board at <= n knight's moves from a fixed square.. |
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+0
7
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| 1, 9, 41, 109, 205, 325, 473, 649, 853, 1085, 1345, 1633, 1949, 2293, 2665, 3065, 3493, 3949, 4433, 4945, 5485, 6053, 6649, 7273, 7925, 8605, 9313, 10049, 10813, 11605, 12425, 13273, 14149, 15053, 15985, 16945, 17933, 18949, 19993, 21065, 22165
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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Erich Friedman, Illustration of initial terms
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FORMULA
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G.f.: (1+5*x+12*x^2-8*x^4+4*x^5)*(1+x)/(1-x)^3;.
a(n)=1-6*n+14*n^2+4*Sign[n(n-1)(n-3)]. - Zak Seidov (zakseidov(AT)yahoo.com), Mar 01 2005
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MAPLE
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(1+5*x+12*x^2-8*x^4+4*x^5)*(1+x)/(1-x)^3;
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MATHEMATICA
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Table[1-6 n+14 n^2+4 Sign[n(n-1)(n-3)], {n, 0, 50}] (Seidov)
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CROSSREFS
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Cf. A018842, A098498.
Sequence in context: A000451 A000437 A095809 this_sequence A001846 A034441 A056243
Adjacent sequences: A018833 A018834 A018835 this_sequence A018837 A018838 A018839
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Marc LeBrun (mlb(AT)well.com)
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EXTENSIONS
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More terms from Zak Seidov (zakseidov(AT)yahoo.com), Mar 01 2005
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