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

1,2

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