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 A152113 A001333 with terms repeated. 3
 1, 1, 3, 3, 7, 7, 17, 17, 41, 41, 99, 99, 239, 239, 577, 577, 1393, 1393, 3363, 3363, 8119, 8119, 19601, 19601, 47321, 47321, 114243, 114243, 275807, 275807, 665857, 665857, 1607521, 1607521, 3880899, 3880899, 9369319, 9369319, 22619537, 22619537, 54608393 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Suggested by an email message from Hugo van der Sanden, Mar 23 2009, who says: Consider the partitions of a 2 x n rectangle into connected pieces consisting of unit squares cut along lattice lines. Then a(n) is the number of distinct pieces with rotational symmetry that extend to opposite corners. LINKS Index entries for linear recurrences with constant coefficients, signature (0,2,0,1). FORMULA a(n) = 2*a(n-2)+a(n-4). G.f.: -x*(x+1)*(x^2+1) / (x^4+2*x^2-1). - Colin Barker, Jul 14 2013 EXAMPLE Example: the pieces illustrating a(3) = 3 are: AAA BB. .CC AAA .BB CC. CROSSREFS Cf. A001333, A078469, A152124. Sequence in context: A174583 A226781 A147144 * A146149 A263795 A070925 Adjacent sequences:  A152110 A152111 A152112 * A152114 A152115 A152116 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Sep 21 2009 STATUS approved

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Last modified January 16 19:49 EST 2019. Contains 319206 sequences. (Running on oeis4.)