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%I #24 Nov 29 2021 01:39:17
%S 47,107,167,263,347,359,467,479,563,863,887,983,1019,1187,1283,1907,
%T 2039,2063,2099,2447,2819,2879,3023,3167,3203,3623,3803,3947,4139,
%U 4919,5387,5399,5507,5879,6599,6659,6983,7079,7187,7523,7559,7703,8423,8699,8963
%N Numbers m such that m, m-1 and m-2 are 1,2,3-almost primes respectively.
%C m-2 is multiple of 3.
%C m is of the form 12k-1.
%C This sequence is subset of A005385.
%C Following a suggestion of _Claudio Meller_.
%H Vincenzo Librandi, <a href="/A201147/b201147.txt">Table of n, a(n) for n = 1..8400</a>
%e 2099 is prime, 2098=2*1049 is semiprime, 2097=3*3*233 is 3-almost prime.
%t primeCount[n_] := Plus @@ Transpose[FactorInteger[n]][[2]]; Select[Range[10000], primeCount[#] == 1 && primeCount[#-1] == 2 && primeCount[#-2] == 3 &] (* _T. D. Noe_, Nov 28 2011 *)
%t Select[Range[10000],PrimeOmega[Range[#,#+2]]=={3,2,1}&]+2 (* _Harvey P. Dale_, Dec 10 2011 *)
%o (PARI) list(lim)=my(v=List(),L=(lim-2)\3,t); forprime(p=3,L\3, forprime(q=3,min(p,L\p), t=3*p*q+2; if(isprime(t) && isprime((t-1)/2), listput(v,t)))); Set(v) \\ _Charles R Greathouse IV_, Feb 01 2017
%Y Cf. A005385, A005383, A112998, A113000, A113008, A072875, A093552.
%K nonn
%O 1,1
%A _Antonio Roldán_, Nov 27 2011
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