

A173569


Least number k such that the function described in A137921 equals n.


4



1, 3, 8, 15, 24, 36, 48, 72, 96, 140, 120, 180, 280, 240, 336, 420, 360, 480, 672, 864, 900, 720, 840, 1008, 1080, 1260, 1980, 1440, 2340, 1680, 3744, 2160, 3024, 2880, 4032, 2520, 3780, 3360, 4680, 4320, 6048, 9450, 9072, 6300, 7200, 6720, 5040, 8640
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


LINKS

Robert G. Wilson v, Table of n, a(n) for n = 1..2665 .


MATHEMATICA

f[n_] := Length@ Split[ Divisors@n, #2  #1 == 1 &] (* f(n) from Dr. Bobby R. Treat *); t = Table[0, {100}]; k = 1; While[k < 10^9, a = f@k; If[a < 101 && t[[a]] == 0, t[[a]] = k; Print[{k, a}]]; k++ ]; t


CROSSREFS

Cf. A137921, A173570.
Cf. A137921: a(n) = number of "divisor islands" of n. A divisor island is any set of consecutive divisors of a number where no pairs of consecutive divisors in the set are separated by 2 or more. [From Robert G. Wilson v, May 20 2010]
Sequence in context: A067998 A066079 A185079 * A173570 A060615 A274696
Adjacent sequences: A173566 A173567 A173568 * A173570 A173571 A173572


KEYWORD

nonn


AUTHOR

Robert G. Wilson v, Feb 22 2010


STATUS

approved



