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 A261204 Number of binary strings of length n that avoid the pattern x x^R x (x^R is the reversal of x). 1
 1, 2, 4, 6, 10, 16, 24, 34, 50, 72, 100, 138, 188, 254, 342, 454, 598, 784, 1018, 1316, 1694, 2166, 2756, 3492, 4404, 5530, 6920, 8626, 10712, 13264, 16368, 20134, 24700, 30212, 36856, 44850, 54438, 65918, 79642, 96008, 115488, 138642, 166100, 198614, 237062 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Giovanni Resta, Table of n, a(n) for n = 0..100 James D. Currie, Narad Rampersad, Binary words avoiding x x^R x and strongly unimodal sequences, arXiv:1508.02964 [math.CO], 2015. James D. Currie, Narad Rampersad, Binary words avoiding x x^R x and strongly unimodal sequences, Journal of Integer Sequences, Vol. 18 (2015), Article 15.10.3. EXAMPLE For n = 6, the substrings to be avoided are 000, 111, 011001, and 100110. There are 26 binary strings that avoid 000 and 111, so there are 26 - 2 = 24 binary strings of length 6 that avoid x x^R x. CROSSREFS Cf. A028445, A241903. Sequence in context: A327047 A332281 A241903 * A293422 A132002 A098151 Adjacent sequences: A261201 A261202 A261203 * A261205 A261206 A261207 KEYWORD nonn AUTHOR Narad Rampersad, Aug 11 2015 EXTENSIONS a(25)-a(44) from Giovanni Resta, Aug 12 2015 STATUS approved

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Last modified June 3 14:00 EDT 2023. Contains 363110 sequences. (Running on oeis4.)