%I #5 Mar 31 2012 10:32:41

%S 4,6,9,15,30,105,420,1155,2310,15015,30030,255255,1021020,4849845,

%T 19399380,111546435,669278610,9704539845,38818159380,100280245065,

%U 601681470390,14841476269620,18551845337025,152125131763605

%N Increasing sequence obtained by union of two sequences A136353 and {b(n)}, where b(n) is the smallest composite number m such that m-1 is prime and the set of distinct prime factors of m consists of the first n primes.

%C This sequence is different from A070826 and A118750

%e a(4)=15 because k=2 and prime factors are 3 and 5; 15 is odd and n-2=13, prime.

%t Contribution from _Farideh Firoozbakht_, Aug 13 2009: (Start)

%t a[n_]:=(c=Product[Prime[k],{k,n}]; For[m=1,!(!PrimeQ[c*m]&&PrimeQ[c*m-1]

%t &&Length[FactorInteger[c*m]]==n),m++ ]; c*m); b[n_]:=(c=Product[Prime[k],

%t {k,2,n+1}]; For[m=1,!(!PrimeQ[c(2m-1)]&&PrimeQ[c(2m-1)-2]&&Length[FactorInteger

%t [c(2*m-1)]]==n),m++ ]; c(2m-1)); Take[Union[Table[a[k],{k,24}],Table[b[k],

%t {k,24}]],24] (End)

%Y Cf. A136349-A136355 A136357-A136358 A070826 A118750.

%K easy,nonn

%O 1,1

%A _Enoch Haga_, Dec 25 2007

%E Edited, corrected and extended by _Farideh Firoozbakht_, Aug 13 2009