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 A284840 Number of quinternary strings avoiding consecutive digits i,i+1 and i,i+2. 2
 1, 5, 18, 63, 224, 799, 2846, 10132, 36073, 128438, 457304, 1628224, 5797263, 20641062, 73492179, 261667749, 931663897, 3317174627, 11810748015, 42051982296, 149725420655, 533095002085, 1898076358760, 6758070980980, 24062005289281, 85672390859855 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (5,-7,8,-5,1). FORMULA G.f.: -1/(x^5-5*x^4+8*x^3-7*x^2+5*x-1). EXAMPLE a(2) = 18: 00, 03, 04, 10, 11, 14, 20, 21, 22, 30, 31, 32, 33, 40, 41, 42, 43, 44. MAPLE a:= n->(<<0|1|0|0|0>, <0|0|1|0|0>, <0|0|0|1|0>,          <0|0|0|0|1>, <1|-5|8|-7|5>>^n)[5\$2]: seq(a(n), n=0..30); CROSSREFS Cf. A277668. Sequence in context: A121050 A029869 A033453 * A301749 A222373 A147535 Adjacent sequences:  A284837 A284838 A284839 * A284841 A284842 A284843 KEYWORD nonn,easy AUTHOR Alois P. Heinz, Apr 03 2017 STATUS approved

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Last modified April 8 08:54 EDT 2020. Contains 333313 sequences. (Running on oeis4.)