OFFSET
1,8
COMMENTS
The nontrivial divisors of n are row n of A163870.
EXAMPLE
The nontrivial divisors of 272 are {2, 4, 8, 16, 17, 34, 68, 136} with divisibility chains {{2, 4, 8, 16}, {17, 34, 68, 136}}, so a(272) = 4.
MATHEMATICA
Table[Switch[n, 1, 0, _?PrimeQ, 0, _, Max@@Length/@Split[DeleteCases[Divisors[n], 1|n], Divisible[#2, #1]&]], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 14 2019
STATUS
approved