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 A080905 Sequence of run lengths in first differences of A080900. 4
 4, 1, 4, 1, 4, 1, 2, 1, 1, 1, 2, 1, 4, 1, 4, 1, 2, 1, 1, 1, 2, 1, 4, 1, 4, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 4, 1, 4, 1, 2, 1, 1, 1, 2, 1, 4, 1, 4, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 4, 1, 4, 1, 2, 1, 1, 1, 2, 1, 4, 1, 4, 1, 2, 1, 1, 1, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Even after 400000 terms there is no clear pattern here. LINKS Antti Karttunen, Table of n, a(n) for n = 1..102526 EXAMPLE A080900 begins 1, 6, 11, 16, 21, 19, 24, 29, 34, 39, 37, 42, 47, 52, 57, 55, 60, 65, ..., the differences are 5, 5, 5, 5, -2, 5, 5, 5, 5, -2, ... with runs of lengths 4, 1, 4, 1, ... PROG (PARI) up_to = 20000; A080905list(up_to_n) = { my(xs=Map(), v, d, ds=vector(up_to_n)); mapput(xs, 1, 1); v = 1; for(n=2, 1+up_to_n, v += (d=if(mapisdefined(xs, n), -2, +5)); mapput(xs, v, n); ds[n-1] = d); my(runlens=List([]), rl=1); for(i=2, #ds, if(ds[i]==ds[i-1], rl++, listput(runlens, rl); rl=1)); Vec(runlens); }; v080905 = A080905list(up_to); A080905(n) = v080905[n]; \\ Antti Karttunen, Feb 24 2020 CROSSREFS Cf. A080900, A080922, A080927. Sequence in context: A144865 A096622 A331291 * A010685 A174571 A099301 Adjacent sequences:  A080902 A080903 A080904 * A080906 A080907 A080908 KEYWORD nonn AUTHOR N. J. A. Sloane, Apr 01 2003 STATUS approved

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Last modified March 29 02:19 EDT 2020. Contains 333104 sequences. (Running on oeis4.)