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%I #19 Jun 28 2014 08:31:44
%S 35,57,1317,1923,2329,2931,4143,5359,5961,6167,7379,8997,103107,
%T 131137,181191,193197,211223,227229,281283,307311,347349,367373,
%U 379383,383389,421431,443449,503509,547557,557563,577587,587593,593599,607613,619631,641643,691701,709719
%N Semiprimes which are concatenation of two consecutive primes.
%C The semiprimes in A045533.
%H K. D. Bajpai, <a href="/A244057/b244057.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a>
%H <a href="/index/Se#semiprime">Index entries for sequences related to semiprimes</a>
%e 35 is in the sequence because the concatenation of [3, 5] = 35 = 5 * 7, which is semiprime.
%e 1923 is in the sequence because concatenation of [19, 23] = 1923 = 3 * 641, which is semiprime.
%e 1113 is not in the sequence because, though 1113 is concatenation of two consecutive primes [11, 13], 1113 = 3 * 7 * 53, which is not semiprime.
%p with(numtheory):with(StringTools):A244057:= proc() local a,b,k; a:=ithprime(n); b:=ithprime(n+1); k:=parse(cat(a,b)); if bigomega(k)=2 then RETURN (k); fi; end: seq(A244057 (), n=1..200);
%t A244057 = {}; Do[t = FromDigits[Flatten[IntegerDigits /@ {Prime[n], Prime[n + 1]}]]; If [PrimeOmega[t] == 2, AppendTo[A244057, t]], {n, 100}]; A244057
%Y Cf. A000040, A001358, A030469, A045533, A244007.
%K nonn,base
%O 1,1
%A _K. D. Bajpai_, Jun 18 2014
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