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

44, 66, 99, 494, 646, 946, 964, 969, 994, 4646, 4669, 4949, 4966, 4994, 4996, 6446, 6466, 6494, 6946, 6964, 6969, 6994, 9494, 9499, 9644, 9669, 9694, 9699, 9994, 44446, 44466, 44644, 44666, 44994, 46446, 46466, 46646, 46669, 46694, 46699, 46949

Offset: 1

Author

Jonathan Vos Post, Nov 15 2005

Keywords

• base
• easy
• nonn

Examples

			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.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

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

Programs

Mathematica

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

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

Extensions

Corrected by Ray Chandler, Nov 19 2005