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%I #9 Oct 13 2019 10:19:48
%S 4198,33262,1564258,6672202,7566178,18181978,20193022,178433278,
%T 187466722,229580146,293158126,467821918,1125878062,1341880018,
%U 4317369778,5198554618,8493529942,10138087306,10594343758,20940647698
%N Semiprimes of the form prime(n)*prime(n+1)*prime(n+2) - 1.
%C This is the three-consecutive-prime minus one equivalent of A103533, which is Giovanni Teofilatto's two-consecutive-prime minus one sequence.
%e n: prime(n) * prime(n+1) * prime(n+2) - 1
%e 6: 13 *17 *19 - 1 = 4198 = 2 * 2099
%e 10: 29 * 31 * 37 - 1 = 33262 = 2 * 16631
%e 29: 109 * 113 * 127 - 1 = 1564258 = 2 * 782129
%e 42: 181 * 191 * 193 -1 = 6672202 = 2 * 3336101
%e 44: 193 * 197 * 199 -1 = 7566178 = 2 * 3783089
%e 55: 257 * 263 * 269 -1 = 18181978 = 2 * 9090989
%e 57: 269 * 271 * 277 -1 = 20193022 = 2 * 10096511
%e 102: 557 * 563 * 569 -1 = 178433278 = 2 * 89216639
%t Bigomega[n_]:=Plus@@Last/@FactorInteger[n]; SemiprimeQ[n_]:=Bigomega[n]==2; Select[Table[Prime[n]*Prime[n+1]*Prime[n+2]-1, {n, 1000}], SemiprimeQ] (* _Ray Chandler_, Mar 29 2005 *)
%o (PARI) for(n=1,420,if(bigomega(k=prime(n)*prime(n+1)*prime(n+2)-1)==2,print1(k,","))) (Brockhaus)
%Y Cf. A000040, A001358, A006881, A103533, A103746, A104874, A104875.
%K easy,nonn
%O 1,1
%A _Jonathan Vos Post_, Mar 24 2005
%E Extended by _Ray Chandler_ and _Klaus Brockhaus_, Mar 29 2005
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