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A182180 Semiprimes that become prime when their digits are sorted into nonincreasing order.

%I A182180 #29 May 17 2015 13:19:53
%S A182180 14,34,35,38,118,119,121,133,134,142,143,145,146,166,194,214,215,218,
%T A182180 314,334,341,346,358,361,365,377,386,395,398,413,415,437,451,473,514,
%U A182180 517,538,583,614,634,635,671,734,737,778,779,791,799,818,835,838,878,893
%N A182180 Semiprimes that become prime when their digits are sorted into nonincreasing order.
%C A182180 Suggested by _Kevin L. Schwartz_.
%H A182180 Alois P. Heinz, <a href="/A182180/b182180.txt">Table of n, a(n) for n = 1..1000</a>
%e A182180 a(10) = 121 = 11*11, which becomes the prime 211 when its digits are sorted into nonincreasing order.
%p A182180 h:= proc(m) local k; for k from m+1 while isprime(k) or
%p A182180             add(i[2], i=ifactors(k)[2])<>2 do od; k
%p A182180     end:
%p A182180 a:= proc(n) option remember; local k;
%p A182180       k:= h(a(n-1));
%p A182180       do if isprime(parse(cat(sort(convert(k, base, 10), `>`)[])))
%p A182180             then return k else k:=h(k) fi
%p A182180       od
%p A182180     end: a(0):=0:
%p A182180 seq(a(n), n=1..80);  # _Alois P. Heinz_, Apr 23 2012
%Y A182180 Cf. A000040, A001358, A115670 Semiprimes (A001358) whose digit reversal is prime, A182150 Semiprimes that are also semiprime when their digits are sorted into nondecreasing order.
%K A182180 nonn,base,easy
%O A182180 1,1
%A A182180 _Jonathan Vos Post_, Apr 23 2012
%E A182180 More terms from _Alois P. Heinz_, Apr 23 2012