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A152617 Smallest number m such that m has exactly n distinct prime factors and sigma(m) has exactly n distinct prime factors. 0
2, 6, 60, 1140, 22230, 778050, 28787850, 1237877550, 82937795850, 6054459097050, 802693813972050, 126022928793611850 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(13) <= 20541737393358731550. a(14) <= 3553720569051060558150. - Donovan Johnson, Jul 13 2011

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

a(9) = 82937795850 = 2*3^2*5^2*7*13*19*37*43*67 (9 distinct prime factors). Sigma(82937795850) = 307906959360 = 2^11*3*5*7*11*13*17*19*31 (9 distinct prime factors).

CROSSREFS

Cf. A000203, A001221.

Sequence in context: A180402 A089039 A156451 * A156472 A108640 A084971

Adjacent sequences:  A152614 A152615 A152616 * A152618 A152619 A152620

KEYWORD

nonn

AUTHOR

Donovan Johnson, Dec 13 2008

EXTENSIONS

a(12) from Donovan Johnson, Jul 13 2011

STATUS

approved

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Last modified October 23 16:46 EDT 2019. Contains 328373 sequences. (Running on oeis4.)