login
A327393
Maximum stable divisor of n.
6
1, 2, 3, 4, 5, 3, 7, 8, 9, 5, 11, 4, 13, 7, 15, 16, 17, 9, 19, 5, 7, 11, 23, 8, 25, 13, 27, 7, 29, 15, 31, 32, 33, 17, 35, 9, 37, 19, 13, 8, 41, 7, 43, 11, 45, 23, 47, 16, 49, 25, 51, 13, 53, 27, 55, 8, 19, 29, 59, 15, 61, 31, 9, 64, 13, 33, 67, 17, 69, 35, 71
OFFSET
1,2
COMMENTS
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798. A number is stable if its distinct prime indices are pairwise indivisible. Stable numbers are listed in A316476, which is the union of this sequence without 1.
EXAMPLE
The stable divisors of 60 are {1, 2, 3, 4, 5, 15}, so a(60) = 15.
MATHEMATICA
stableQ[u_, Q_]:=!Apply[Or, Outer[#1=!=#2&&Q[#1, #2]&, u, u, 1], {0, 1}];
Table[Max[Select[Divisors[n], stableQ[PrimePi/@First/@FactorInteger[#], Divisible]&]], {n, 100}]
CROSSREFS
See link for additional cross-references.
Sequence in context: A346596 A324388 A309639 * A376368 A376664 A217434
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 15 2019
STATUS
approved