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A111494 3-almost primes with semiprime digits (digits 4, 6, 9 only). 9

%I #9 Jan 08 2019 20:22:27

%S 44,66,99,494,646,946,964,969,994,4646,4669,4949,4966,4994,4996,6446,

%T 6466,6494,6946,6964,6969,6994,9494,9499,9644,9669,9694,9699,9994,

%U 44446,44466,44644,44666,44994,46446,46466,46646,46669,46694,46699,46949

%N 3-almost primes with semiprime digits (digits 4, 6, 9 only).

%H Charles R Greathouse IV, <a href="/A111494/b111494.txt">Table of n, a(n) for n = 1..10000</a>

%e a(1) = 44 = 2^2 * 11, a(2) = 66 = 2 * 3 * 11, a(3) = 99 = 3^2 * 11, a(4) = 494 = 2 * 13 * 19, a(5) = 646 = 2 * 17 * 19, a(6) = 946 = 2 * 11 * 43, a(7) = 964 = 2^2 * 241, a(8) = 969 = 3 * 17 * 19, a(9) = 994 = 2 * 7 * 71, a(10) = 4646 = 2 * 23 * 101, a(11) = 4669 = 7 * 23 * 29.

%t Table[Select[FromDigits/@Tuples[{4,6,9},n],PrimeOmega[#]==3&],{n,5}]// Flatten (* _Harvey P. Dale_, Jan 08 2019 *)

%o (PARI) do(N)=my(v=List(),a=[4,6,9]); for(d=1,N, forvec(u=vector(d,i,[1,3]), t=fromdigits(apply(n->a[n],u)); if(bigomega(t)==3, listput(v,t)))); Set(v) \\ _Charles R Greathouse IV_, Feb 01 2017

%Y Cf. A001358, A014612, A107665, A107666, A107342, A111496, A111697.

%K base,easy,nonn

%O 1,1

%A _Jonathan Vos Post_, Nov 15 2005

%E Corrected by _Ray Chandler_, Nov 19 2005

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)