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A080371 a(n) = smallest x such that quotient d(x+1)/d(x) equals n, where d()=A000005, the number of divisors. 2
2, 1, 11, 23, 47, 59, 191, 167, 179, 239, 5119, 359, 20479, 2111, 719, 839, 983039, 1259, 786431, 3023, 2879, 15359, 62914559, 3359, 22031, 266239, 6299, 6719, 13690208255, 5039, 22548578303, 7559, 156671, 6881279, 25919, 10079 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(37) > 10^12. - Donovan Johnson, Sep 02 2013

LINKS

Table of n, a(n) for n=1..36.

Donovan Johnson, All 435 terms <= 10^12

FORMULA

a(n)=Min{x : d[x+1]/d[x]=n}

EXAMPLE

n = 49: a(49) = 233279 = m, d(m+1) = 98, d(m) = 2, quotient = 49.

MATHEMATICA

t = Table[ 0, {50}]; Do[ s = DivisorSigma[0, n+1] / DivisorSigma[0, n]; If[ s < 51 && t[[s]] == 0, t[[s]] = n], {n, 1, 10^8}]; t

CROSSREFS

Cf. A000005, A080372.

Sequence in context: A305877 A111724 A184299 * A151337 A013019 A012904

Adjacent sequences:  A080368 A080369 A080370 * A080372 A080373 A080374

KEYWORD

nonn

AUTHOR

Labos Elemer, Feb 24 2003

EXTENSIONS

More terms from Robert G. Wilson v, Feb 27 2003

The sequence continues: ?, 5039, ?, 7559, 156671, 6881279, 25919, 10079, ?, 5505023, ...

a(29) and a(31) from Donovan Johnson, Dec 26 2012

STATUS

approved

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Last modified October 20 04:37 EDT 2018. Contains 316378 sequences. (Running on oeis4.)