A136355 Numbers of the form P = product of the first k odd primes where P+2 is composite.

1155, 255255, 4849845, 111546435, 152125131763605, 6541380665835015, 16294579238595022365, 58644190679703485491635, 3929160775540133527939545, 278970415063349480483707695, 20364840299624512075310661735, 1608822383670336453949542277065

Offset: 1

Author

Enoch Haga, Dec 25 2007

Keywords

• easy
• nonn

Comments

This sequence is different from A070826 and A118750.

Examples

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

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..332

Crossrefs

Cf. A136349-A136354, A136356-A136358, A070826, A118750.

Programs

Mathematica

v=Select[Range[21],!PrimeQ[Product[Prime[k+1],{k,#}]+2]&]; Table[Product[Prime[k+1],{k,v[[t]]}],{t,Length[v]}] (* Farideh Firoozbakht, Aug 12 2009 *)
Select[FoldList[Times,Prime[Range[2,22]]],CompositeQ[#+2]&] (* Harvey P. Dale, Jun 08 2022 *)

Extensions

Edited with more terms by Farideh Firoozbakht, Aug 12 2009