A136355 - OEIS

%I #9 Jun 08 2022 13:43:03

%S 1155,255255,4849845,111546435,152125131763605,6541380665835015,

%T 16294579238595022365,58644190679703485491635,

%U 3929160775540133527939545,278970415063349480483707695,20364840299624512075310661735

%N Numbers of the form P = product of the first k odd primes where P+2 is composite.

%C This sequence is different from A070826 and A118750

%H Harvey P. Dale, <a href="/A136355/b136355.txt">Table of n, a(n) for n = 1..332</a>

%e a(1)=1155 because 1157 is not prime.

%t Contribution from _Farideh Firoozbakht_, Aug 12 2009: (Start)

%t v=Select[Range[20],!PrimeQ[Product[Prime[k+1],{k,#}]+2]&]; Table[Product[Prime

%t [k+1],{k,v[[t]]}],{t,Length[v]}] (End)

%t Select[FoldList[Times,Prime[Range[2,21]]],CompositeQ[#+2]&] (* _Harvey P. Dale_, Jun 08 2022 *)

%Y Cf. A136349-A136354 A136356-A136358 A070826 A118750.

%K easy,nonn

%O 1,1

%A _Enoch Haga_, Dec 25 2007

%E Edited with more terms by _Farideh Firoozbakht_, Aug 12 2009