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A058199 Where d(m) (number of divisors, A000005) falls by at least n. 4
4, 6, 12, 12, 24, 30, 36, 60, 60, 60, 120, 120, 120, 180, 180, 180, 240, 240, 360, 360, 360, 420, 720, 720, 720, 720, 840, 840, 840, 1260, 1260, 1260, 1680, 1680, 1680, 1680, 1680, 2160, 2520, 2520, 2520, 2520, 2520, 2520, 2520, 2520, 5040, 5040, 5040 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, 1996, Section II.1.3.a.

LINKS

T. D. Noe, Table of n, a(n) for n=1..500

FORMULA

A051950(a(n) + 1) <= - n. - Reinhard Zumkeller, Feb 04 2013

EXAMPLE

d(12)=6, d(13)=2 gives first drop of >= 3, so a(3)=a(4)=12.

MATHEMATICA

max = 10^4; dd = Differences[Table[DivisorSigma[0, m], {m, 1, max}]]; a[n_] := Position[dd, d_ /; d <= -n, 1, 1][[1, 1]]; Table[a[n], {n, 1, -Min[dd] }] (* Jean-Fran├žois Alcover, Nov 23 2015 *)

PROG

(Haskell)

import Data.List (findIndex)

import Data.Maybe (fromJust)

a058199 n = fromJust $ findIndex (n <=) $ map negate a051950_list

-- Reinhard Zumkeller, Feb 04 2013

CROSSREFS

Cf. A000005, A058197, A058198.

Sequence in context: A038040 A143356 A058270 * A289535 A310592 A310593

Adjacent sequences:  A058196 A058197 A058198 * A058200 A058201 A058202

KEYWORD

nonn,nice,easy

AUTHOR

N. J. A. Sloane, Nov 28 2000

EXTENSIONS

More terms from James A. Sellers, Nov 29 2000

STATUS

approved

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Last modified January 27 15:14 EST 2020. Contains 331295 sequences. (Running on oeis4.)