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 A187767 Number of bicolored cyclic patterns n X n. 2
 0, 2, 3, 10, 15, 35, 63, 138, 255, 527, 1023, 2083, 4095, 8255, 16383, 32906, 65535, 131327, 262143, 524815, 1048575, 2098175, 4194303, 8390691, 16777215, 33558527, 67108863, 134225983, 268435455, 536887295, 1073741823, 2147516554, 4294967295, 8590000127, 17179869183 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A bicolored cyclic pattern is a 0-1 n x n matrix where the j-th row is equal to the first row rotated to the left by (j-1)*k places, with 1 <= k <= n a parameter. For example, with first row = 0110 we have . . (k=1) 0 1 1 0  (k=2) 0 1 1 0  (k=3) 0 1 1 0  (k=4) 0 1 1 0 .       1 1 0 0        1 0 0 1        0 0 1 1        0 1 1 0 .       1 0 0 1        0 1 1 0        1 0 0 1        0 1 1 0 .       0 0 1 1        1 0 0 1        1 1 0 0        0 1 1 0 The (2^n-2)*n matrices so obtained are reduced considering equivalent those obtained exchanging 0's and 1's and those which produce the same pattern, apart translation. LINKS Andrew Howroyd, Table of n, a(n) for n = 1..200 Giovanni Resta, Picture explaining sequence definition. Giovanni Resta, Pictures for a(2)-a(7). Giovanni Resta, Pictures for a(8) and a(9). FORMULA a(1) = 0; a(n) = 2^(n-1)-1 if n is odd, 2^(n-1)+a(n/2) if n is even (conjectured). a(n) = -1 + Sum_{d|n} d*A000048(d). - Andrew Howroyd, Jun 02 2017 EXAMPLE a(4)=10 is represented below. See Links for more examples. . 1000 0100 0010 0001 0101 1010 1001 0110 1100 0011 . 0100 0001 0100 0001 0101 0101 1100 1100 0011 0011 . 0010 0100 1000 0001 0101 1010 0110 1001 1100 0011 . 0001 0001 0001 0001 0101 0101 0011 0011 0011 0011 MATHEMATICA cyPatt[n_]:=Block[{b, c}, c[v_, q_:1]:=Table[RotateLeft[v, i q], {i, n}]; b=Union[(First@Union[c@#, c[1-#]])& /@ IntegerDigits[Range[2^n/2-1], 2, n]]; Union@Flatten[Table[c[e, j], {j, n}, {e, b}], 1]]; (*count*) a[n_] := Length@cyPatt@n; Print["Seq = ", a/@Range[12]]; (*show*) showP[p_] := GraphicsGrid@Partition[ArrayPlot/@p, 8, 8, 1, Null]; showP[cyPatt[6]] PROG (PARI) b(n)=sumdiv(n, d, (d%2)*(moebius(d)*2^(n/d)))/(2*n); a(n)=sumdiv(n, d, d*b(d)) - 1; \\ Andrew Howroyd, Jun 02 2017 CROSSREFS The number of patterns made of vertical stripes only is A056295(n). Cf. A000048, A056303, A127804. Sequence in context: A075770 A135101 A108065 * A226881 A026336 A027913 Adjacent sequences:  A187764 A187765 A187766 * A187768 A187769 A187770 KEYWORD nonn AUTHOR Giovanni Resta, Jan 04 2013 EXTENSIONS a(22)-a(35) from Andrew Howroyd, Jun 02 2017 STATUS approved

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Last modified July 17 15:19 EDT 2019. Contains 325106 sequences. (Running on oeis4.)