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A060764
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Number of divisors of n which are not also differences between consecutive divisors (ordered by increasing magnitude) of n.
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6
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1, 1, 2, 1, 2, 2, 2, 1, 3, 2, 2, 3, 2, 2, 4, 1, 2, 3, 2, 2, 4, 2, 2, 4, 3, 2, 4, 2, 2, 4, 2, 1, 4, 2, 4, 4, 2, 2, 4, 4, 2, 4, 2, 2, 6, 2, 2, 5, 3, 3, 4, 2, 2, 4, 4, 4, 4, 2, 2, 5, 2, 2, 6, 1, 4, 4, 2, 2, 4, 5, 2, 6, 2, 2, 6, 2, 4, 4, 2, 5, 5, 2, 2, 7, 4, 2, 4, 2, 2, 6, 4, 2, 4, 2, 4, 6, 2, 3, 6, 3, 2, 4, 2, 2, 8
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OFFSET
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1,3
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LINKS
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EXAMPLE
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For n=70, divisors={1,2,5,7,10,14,35,70}; differences={1,3,2,3,4,21,35}; the divisors {5,7,10,14,70} are not differences, so a(70)=5.
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MATHEMATICA
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a[n_] := Length[Complement[d=Divisors[n], Drop[d, 1]-Drop[d, -1]]]
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PROG
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(PARI) A060764(n) = { my(divs=divisors(n), diffs=vecsort(vector(#divs-1, i, divs[i+1]-divs[i]), , 8), c=#divs); for(i=1, #diffs, if(!(n%diffs[i]), c--)); (c); }; \\ Antti Karttunen, Sep 21 2018
(Python)
from itertools import pairwise
from sympy import divisors
e = map(lambda x:x[1]-x[0], pairwise(d:=divisors(n)))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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