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A328162
Maximum length of a divisibility chain of consecutive divisors of n.
8
1, 2, 2, 3, 2, 2, 2, 4, 3, 2, 2, 2, 2, 2, 2, 5, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 4, 3, 2, 2, 2, 6, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 7, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 5, 2, 2, 2, 2, 2, 2
OFFSET
1,2
LINKS
EXAMPLE
The divisors of 968 split into consecutive divisibility chains {{1, 2, 4, 8}, {11, 22, 44, 88}, {121, 242, 484, 968}}, so a(968) = 4.
MAPLE
f:= proc(n) local F, L, d, i;
F:= sort(convert(numtheory:-divisors(n), list));
d:= nops(F);
L:= Vector(d);
L[1]:= 1;
for i from 2 to d do
if F[i] mod F[i-1] = 0 then L[i]:= L[i-1]+1
else L[i]:= 1
fi
od;
max(L)
end proc:
map(f, [$1..100]); # Robert Israel, Apr 20 2023
MATHEMATICA
Table[Max@@Length/@Split[Divisors[n], Divisible[#2, #1]&], {n, 100}]
CROSSREFS
Records occur at powers of 2 (A000079).
Taking only proper divisors gives A328194.
Taking only divisors > 1 gives A328195.
The maximum run-length among divisors of n is A055874.
Sequence in context: A196229 A191302 A161189 * A375767 A375769 A375429
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 06 2019
STATUS
approved