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.

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

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(2m-1)]&&PrimeQ[c
(2m-1)+2]&&Length[FactorInteger[c(2m-1)]]==n), m++ ]; c(2m-1)); Table[a[n], {n, 17}] (End)

Crossrefs

Cf. A136349-A136353 A136355-A136358 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