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 A017629 a(n) = 12*n+9. 16
 9, 21, 33, 45, 57, 69, 81, 93, 105, 117, 129, 141, 153, 165, 177, 189, 201, 213, 225, 237, 249, 261, 273, 285, 297, 309, 321, 333, 345, 357, 369, 381, 393, 405, 417, 429, 441, 453, 465, 477, 489, 501, 513, 525, 537, 549, 561, 573, 585, 597, 609, 621, 633 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Numbers k such that k mod 2 = (k+1) mod 3 = 1 and (k+2) mod 4 <> 1. - Klaus Brockhaus, Jun 15 2004 For n>3, the number of squares on the infinite 3-column chessboard at <=n knight moves from any fixed point. - Ralf Stephan, Sep 15 2004 A089911(2*a(n)) = 4. - Reinhard Zumkeller, Jul 05 2013 LINKS Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (2,-1). FORMULA a(n) = 6*(4n+1)-a(n-1) (with a(0)=9). - Vincenzo Librandi, Dec 17 2010 MATHEMATICA 12*Range[0, 200]+9 (* Vladimir Joseph Stephan Orlovsky, Feb 19 2011*) PROG (Sage) [i+9 for i in range(525) if gcd(i, 12) == 12] # - Zerinvary Lajos, May 21 2009 (Haskell) a017629 = (+ 9) . (* 12)  -- Reinhard Zumkeller, Jul 05 2013 (PARI) a(n)=12*n+9 \\ Charles R Greathouse IV, Jul 10 2016 CROSSREFS Cf. A008594, A017533, A017545. Subsequence of A072065. Cf. A017137, A004767. Sequence in context: A133929 A086470 A176256 * A216240 A176258 A107978 Adjacent sequences:  A017626 A017627 A017628 * A017630 A017631 A017632 KEYWORD nonn,easy AUTHOR STATUS approved

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