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 A006928 a(n) = length of (n+1)st run, with initial terms 1, 2. (Formerly M0070) 24
 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Eric Weisstein's World of Mathematics, Kolakoski Sequence. FORMULA a(n) = A000002(n+1), n > 1. EXAMPLE Start with [ 1,2 ]. a(1)=1, so the second run has length 1, so a(3) must be 1. a(2)=2, so the third run has length 2, so a(4) must also be 1 and a(5) must be 2. a(3)=1, so the 4th run has length 1, so a(6) must be 1; etc. - Labos Elemer MATHEMATICA a = {1, 2}; Do[AppendTo[a, 1+Mod[n, 2]], {n, 2, 80}, {i, a[[n]]}]; a (* Jean-François Alcover, Aug 09 2016, adapted from PARI *) PROG (PARI) a=[ 1, 2 ]; for(n=2, 80, for(i=1, a[ n ], a=concat(a, 1+(n%2)))); a CROSSREFS Essentially the same as Kolakoski sequence A000002. Sequence in context: A248623 A086412 A192006 * A087890 A245077 A008676 Adjacent sequences:  A006925 A006926 A006927 * A006929 A006930 A006931 KEYWORD nonn,easy,nice AUTHOR STATUS approved

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Last modified May 16 16:06 EDT 2022. Contains 353706 sequences. (Running on oeis4.)