A104874 Semiprimes of the form prime(n)*prime(n+1)*prime(n+2)*prime(n+3) - 1.

209, 1154, 645328246, 2445956098, 2337448622686, 19317973275826, 22894376863198, 32220239865718, 51087435019342, 78382834887262, 163068083613646, 176031800345938, 622751201209726, 1292966939911018

Offset

1,1

Comments

This is the four-consecutive-prime minus one equivalent of A103533.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

n: prime(n) * prime(n+1) * prime(n+2) * prime(n+3) - 1
1: 2 * 3 * 5 * 7 - 1 = 209 = 11 * 19
2: 3 * 5 * 7 * 11 - 1 = 1154 = 2 * 577
36: 151 * 157 * 163 * 167 - 1 = 645328246 = 2 * 322664123
47: 211 * 223 * 227 * 229 - 1 = 2445956098 = 2 * 1222978049
201: 1229 * 1231 * 1237 * 1249 - 1 = 2337448622686 = 2 * 1168724311343.

Mathematica

Bigomega[n_]:=Plus@@Last/@FactorInteger[n]; SemiprimeQ[n_]:=Bigomega[n]==2; Select[Table[Prime[n]*Prime[n+1]*Prime[n+2]*Prime[n+3]-1, {n, 1000}], SemiprimeQ] (* Ray Chandler, Mar 29 2005 *)

Crossrefs

Cf. A000040, A001358, A006881, A103533, A103614, A103746, A104875.

Sequence in context: A203041 A293981 A181623 * A157441 A304063 A305455

Adjacent sequences: A104871 A104872 A104873 * A104875 A104876 A104877

Keyword

easy,nonn

Author

Jonathan Vos Post, Mar 29 2005

Extensions

Extended by Ray Chandler, Mar 29 2005

Status

approved