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

Author

Enoch Haga, Dec 25 2007

Keywords

• easy
• nonn

Comments

This sequence is different from A070826 and A118750.

Examples

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

Crossrefs

Cf. A136349-A136353, A136355-A136358, A070826, A118750.

Programs

Mathematica

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}] (* Farideh Firoozbakht, Aug 12 2009 *)

Extensions

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