login
A328450
Numbers that are a smallest number with k pairs of successive divisors, for some k.
4
1, 2, 6, 12, 60, 72, 180, 360, 420, 840, 1260, 2520, 3780, 5040, 13860, 27720, 36960, 41580, 55440, 83160, 166320, 277200, 360360, 471240, 491400, 720720, 1081080, 1113840, 2162160, 2827440, 3341520, 4324320, 5405400, 6126120
OFFSET
0,2
COMMENTS
A sorted version of A287142.
EXAMPLE
The divisors of 72 are {1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72}, with pairs of successive divisors {{1, 2}, {2, 3}, {3, 4}, {8, 9}}, and no smaller number has 4 successive pairs, so 72 belongs to the sequence.
MATHEMATICA
dat=Table[Count[Differences[Divisors[n]], 1], {n, 10000}];
Sort[Table[Position[dat, i][[1, 1]], {i, Union[dat]}]]
CROSSREFS
Sorted positions of first appearances in A129308.
The longest run of divisors of n has length A055874(n).
Numbers whose divisors > 1 have no non-singleton runs are A088725.
The Heinz number of the multiset of run-lengths of divisors of n is A328166(n).
The smallest number whose divisors have a longest run of length n is A328449(n).
Sequence in context: A072181 A283487 A126915 * A322381 A265125 A328549
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 15 2019
STATUS
approved