A080905 - OEIS

A080905

Sequence of run lengths in first differences of A080900.

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

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