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A182150 Semiprimes that are also semiprime when their digits are sorted into nondecreasing order.

%I A182150 #29 May 17 2015 11:31:38
%S A182150 4,6,9,14,15,22,25,26,33,34,35,38,39,46,49,51,55,57,58,62,69,77,85,93,
%T A182150 94,111,115,118,119,122,123,129,133,134,143,145,146,155,158,159,166,
%U A182150 169,177,178,185,187,202,205,206,213,219,221,226,235,237,247,249,253
%N A182150 Semiprimes that are also semiprime when their digits are sorted into nondecreasing order.
%C A182150 This is to A211654 primes that are also prime when their digits are sorted into nondecreasing order as A001358 semiprimes are to A000040 primes. There is an ambiguity arising from OEIS conventions, exemplified by the semiprime 303, which sorts to 033 and truncates to the semiprime 33.
%H A182150 Alois P. Heinz, <a href="/A182150/b182150.txt">Table of n, a(n) for n = 1..1000</a>
%e A182150 51 is in the sequence because, though it is a semiprime whose digits are in descending order, once the digits are sorted to be nondecreasing, it is the semiprime 15, whose digits are (left to right) nondecreasing.
%p A182150 h:= proc(m) local k; for k from m+1 while isprime(k) or
%p A182150             add(i[2], i=ifactors(k)[2])<>2 do od; k
%p A182150     end:
%p A182150 a:= proc(n) option remember; local k, l, s;
%p A182150       k:= h(a(n-1));
%p A182150       do l:= sort(convert(k, base, 10));
%p A182150          s:= add(l[i]*10^(nops(l)-i), i=1..nops(l));
%p A182150          if h(s-1)=s then return k else k:=h(k) fi
%p A182150       od
%p A182150     end: a(0):=0:
%p A182150 seq(a(n), n=1..100);  # _Alois P. Heinz_, Apr 22 2012
%t A182150 Select[Range[300],PrimeOmega[#]==2&&PrimeOmega[FromDigits[ Sort[ IntegerDigits[ #]]]]==2&] (* _Harvey P. Dale_, Nov 13 2014 *)
%Y A182150 Cf. A001358, A097393, A211654.
%K A182150 nonn,base,easy
%O A182150 1,1
%A A182150 _Jonathan Vos Post_, Apr 18 2012
%E A182150 More terms from _Alois P. Heinz_, Apr 22 2012