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A080905
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Sequence of run lengths in first differences of A080900.
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4
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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
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OFFSET
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1,1
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COMMENTS
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Even after 400000 terms there is no clear pattern here.
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LINKS
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Antti Karttunen, Table of n, a(n) for n = 1..102526
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EXAMPLE
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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, ...
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PROG
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(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
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CROSSREFS
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Cf. A080900, A080922, A080927.
Sequence in context: A144865 A096622 A331291 * A010685 A174571 A099301
Adjacent sequences: A080902 A080903 A080904 * A080906 A080907 A080908
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Apr 01 2003
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STATUS
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approved
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