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 A261212 Maximum number of 1's in an fully symmetrical n X n binary matrix with no three 1's adjacent in a line along a row, column or diagonally. 1
 1, 4, 4, 8, 16, 20, 25, 36, 41, 48, 64, 72, 81, 100, 109, 120, 144, 156, 173, 196, 213, 228, 256, 272, 300, 324, 349, 368, 401, 424, 457, 484 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Fully symmetrical refers to the four symmetry axes: horizontal, vertical and two diagonal. Note that a(3k+2) = 4*(1+k)^2, for k=0,...,8, but a(29) = 401. LINKS Giovanni Resta, Illustration of a(6)-a(30) FORMULA a(n) <= A181018(n). a(3k+2) >= 4*(k+1)^2. EXAMPLE For n=4, the matrix is 0 1 0 1 0 1 0 1 0 For n=6, the matrix is 1 1 0 0 1 1 1 0 1 1 0 1 0 1 0 0 1 0 0 1 0 0 1 0 1 0 1 1 0 1 1 1 0 0 1 1 CROSSREFS Cf. A181018. Sequence in context: A190100 A244421 A030168 * A112435 A232508 A028610 Adjacent sequences:  A261209 A261210 A261211 * A261213 A261214 A261215 KEYWORD nonn AUTHOR V.J. Pohjola and Giovanni Resta, Aug 12 2015 STATUS approved

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Last modified March 30 06:40 EDT 2020. Contains 333119 sequences. (Running on oeis4.)