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A052215 a(n) = smallest number m such that m and m+1 are the product of exactly n distinct primes. 8
2, 14, 230, 7314, 378014, 11243154, 965009045, 65893166030, 5702759516090, 605247139068494, 78971815814237709 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Prime factors may not be repeated in m and m+1. The difference between this sequence and A093548 is that in the latter, prime factors may be repeated. So the present sequence imposes more stringent conditions than A093548, hence a(n) >= A093548(n). - N. J. A. Sloane, Nov 21 2015

A115186(n) <= A093548 (n) <= a(n). - Zak Seidov, Jan 16 2015

2^63 < a(12) <= 22593106657425552170. [From Donovan Johnson, Oct 23 2008]

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

14 and 15 are both the product of 2 primes

230 is the 3rd entry because we have (230=2*5*23, 231=3*7*11).

CROSSREFS

Cf. A093548 (another version), A093549, A093550, A115186, A318896.

Sequence in context: A118086 A048163 A093548 * A053846 A053855 A219344

Adjacent sequences:  A052212 A052213 A052214 * A052216 A052217 A052218

KEYWORD

hard,nice,nonn

AUTHOR

Erich Friedman, Jan 29 2000

EXTENSIONS

More terms from Naohiro Nomoto, Jul 08 2001

a(7) from Farideh Firoozbakht, Apr 06 2004

a(8)-a(10) from Martin Fuller, Jan 17 2006

a(11) from Donovan Johnson, Oct 23 2008

STATUS

approved

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Last modified February 15 20:49 EST 2019. Contains 320138 sequences. (Running on oeis4.)