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 A201147 Numbers n such that n, n-1 and n-2 are 1,2,3-almost primes respectively. 2
 47, 107, 167, 263, 347, 359, 467, 479, 563, 863, 887, 983, 1019, 1187, 1283, 1907, 2039, 2063, 2099, 2447, 2819, 2879, 3023, 3167, 3203, 3623, 3803, 3947, 4139, 4919, 5387, 5399, 5507, 5879, 6599, 6659, 6983, 7079, 7187, 7523, 7559, 7703, 8423, 8699, 8963 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n-2 is multiple of 3. n is  of the form 12k-1. This sequence is subset of A005385. Following a suggestion of Claudio Meller. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..8400 EXAMPLE 2099 is prime, 2098=2*1049 is semiprime, 2097=3*3*233 is 3-almost prime. MATHEMATICA primeCount[n_] := Plus @@ Transpose[FactorInteger[n]][[2]]; Select[Range[10000], primeCount[#] == 1 && primeCount[#-1] == 2 && primeCount[#-2] == 3 &] (* T. D. Noe, Nov 28 2011 *) Select[Range[10000], PrimeOmega[Range[#, #+2]]=={3, 2, 1}&]+2 (* Harvey P. Dale, Dec 10 2011 *) PROG (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 CROSSREFS Cf. A005385, A005383, A112998, A113000, A113008, A072875, A093552. Sequence in context: A124096 A308784 A142796 * A142020 A044234 A044615 Adjacent sequences:  A201144 A201145 A201146 * A201148 A201149 A201150 KEYWORD nonn AUTHOR Antonio Roldán, Nov 27 2011 STATUS approved

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Last modified February 19 13:25 EST 2020. Contains 332044 sequences. (Running on oeis4.)