A173569 Least number k such that the function described in A137921 equals n.

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

Offset: 1

Author

Robert G. Wilson v, Feb 22 2010

Keywords

• nonn

Links

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

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]

Programs

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