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Primes prime(n) such that 10*prime(n)+prime(n+1) is not prime.
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%I #2 Mar 31 2012 14:40:00

%S 3,5,7,11,13,17,19,23,29,37,41,43,53,59,67,71,79,89,97,101,103,107,

%T 109,113,127,137,139,149,163,167,173,179,181,191,193,197,199,223,227,

%U 229,233,239,241,263,269,271,277,281,283,293,307,311,313,317,331,337,347

%N Primes prime(n) such that 10*prime(n)+prime(n+1) is not prime.

%e a(11)=41 because 41 is prime, the nextprime is 43 and 10*41+43=453, 453 = 3*151 is not prime,

%e a(12)=43 because 43 is prime, the nextprime is 47 and 10*43+47=477, 477 = 3^(2)*53 is not prime,

%e a(13)=53 because 53 is prime, the nextprime is 59 and 10*53+59=589, 589 = 19*31 is not prime, ...

%p ts_p5_02:=proc(n) local a,b,i,ans; ans := [ ]: for i from 1 to n do a := 10*ithprime(i)+ithprime(i+1): if (isprime(a)=false) then ans := [ op(ans), ithprime(i) ]: fi od; RETURN(ans) end: ts_p5_02(300);

%Y Cf. A129900.

%K nonn

%O 1,1

%A _Jani Melik_, Aug 01 2007