

A136354


a(n) is the smallest odd composite number m such that m+2 is prime and the set of distinct prime factors of m consists of the first n odd primes.


4



9, 15, 105, 3465, 15015, 765765, 33948915, 334639305, 3234846615, 100280245065, 3710369067405, 1369126185872445, 32706903329175075, 307444891294245705, 211829530101735290745, 961380175077106319535, 762374478836145311391255
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OFFSET

1,1


COMMENTS

This sequence is different from A070826 and A118750


LINKS

Table of n, a(n) for n=1..17.


EXAMPLE

a(1)=9 because k=1 with prime factor 3 and 9+2=11, prime


MATHEMATICA

Contribution from Farideh Firoozbakht, Aug 12 2009: (Start)
a[n_]:=(c=Product[Prime[k], {k, 2, n+1}]; For[m=1, !(!PrimeQ[c(2m1)]&&PrimeQ[c
(2m1)+2]&&Length[FactorInteger[c(2m1)]]==n), m++ ]; c(2m1)); Table[a[n], {n, 17}] (End)


CROSSREFS

Cf. A136349A136353 A136355A136358 A070826 A118750.
Sequence in context: A173037 A029712 A136353 * A177184 A098146 A124274
Adjacent sequences: A136351 A136352 A136353 * A136355 A136356 A136357


KEYWORD

easy,nonn


AUTHOR

Enoch Haga, Dec 25 2007


EXTENSIONS

Edited, corrected and extended by Farideh Firoozbakht, Aug 12 2009


STATUS

approved



