%I #7 Apr 28 2015 15:02:09
%S 23,37,211,223,229,241,271,283,311,313,317,331,337,347,353,359,367,
%T 373,379,383,389,397,523,541,547,571,719,743,761,773,797,1117,1123,
%U 1129,1153,1171,1319,1361,1367,1373,1723,1741,1747,1753,1759,1783,1789,1931
%N Home primes of semiprimes (A001358).
%C Not the same as A133957.
%C Number of terms < 10^n: 0, 2, 31, 223, 1638, 11752, 89918, ....
%t lst = {}; semiPrimeQ[x_] := Plus @@ Last /@ FactorInteger@x == 2; f[n_] := FromDigits@ Flatten[IntegerDigits@ Table[ #[[1]], {#[[2]]}] & /@ FactorInteger@n, 2]; h[n_] := NestWhileList[ f@# &, n, ! PrimeQ@# &, 1, 6];
%Y Cf. A001358, A133955, A133957.
%K nonn,base
%O 1,1
%A _Jonathan Vos Post_ & _Robert G. Wilson v_, Oct 01 2007, Oct 06 2007