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A104875 Semiprimes of the form prime(n)*prime(n+1)*prime(n+2)*prime(n+3)*prime(n+4) - 1. 3

%I #13 Nov 01 2019 10:57:25

%S 15014,1062346,600662302,2224636919002,118335570521086,

%T 168652154886862,3790374062238502,6290838589498366,127018534712243098,

%U 131125107904515418,190740905520325018,2057351971883521282,3151949824862998762

%N Semiprimes of the form prime(n)*prime(n+1)*prime(n+2)*prime(n+3)*prime(n+4) - 1.

%C This is the five-consecutive-prime minus one equivalent of A103533.

%H Vincenzo Librandi, <a href="/A104875/b104875.txt">Table of n, a(n) for n = 1..1000</a>

%e n prime(n) * prime(n+1) * prime(n+2) * prime(n+3) * prime(n+4) - 1

%e 1: 2 * 3 * 5 * 7 * 11 - 1 = 2309 is prime; examples hereafter are semiprime

%e 2: 3 * 5 * 7 * 11 * 13 - 1 = 15014 = 2 * 7507

%e 5: 11 * 13 * 17 * 19 * 23 - 1 = 1062346 = 2 * 531173

%e 15: 47 * 53 * 59 * 61 * 67 - 1 = 600662302 = 2 * 300331151

%e 60: 281 * 283 * 293 * 307 * 311 - 1 = 2224636919002 = 2 * 1112318459501

%e 117: 643 * 647 * 653 * 659 * 661 - 1 = 118335570521086 = 2 * 59167785260543

%t Bigomega[n_]:=Plus@@Last/@FactorInteger[n]; SemiprimeQ[n_]:=Bigomega[n]==2; Select[Table[Prime[n]*Prime[n+1]*Prime[n+2]*Prime[n+3]*Prime[n+4]-1, {n, 1000}], SemiprimeQ] (* _Ray Chandler_, Mar 29 2005 *)

%Y Cf. A000040, A001358, A006881, A103533, A103614, A103746, A104874.

%K easy,nonn

%O 1,1

%A _Jonathan Vos Post_, Mar 29 2005

%E Extended by _Ray Chandler_, Mar 29 2005

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)