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 A187766 Even numbers k such that prime(k) -+ k are both composite. 0

%I

%S 12,20,36,38,40,46,52,56,58,60,62,64,74,78,80,86,88,112,118,120,122,

%T 124,128,132,134,136,138,140,142,146,156,160,162,164,166,170,176,182,

%U 184,186,188,190,194,198,208,210,212,216

%N Even numbers k such that prime(k) -+ k are both composite.

%C Even numbers not in A064269 and not in A064402.

%C Interestingly, prime(12) = 37 and both 37 - 12 = 25 and 37 + 12 = 49 are squares. Is there another such n?

%t Select[2*Range[200],!PrimeQ[Prime[#]+#]&&!PrimeQ[Prime[#]-#]&] (* _Harvey P. Dale_, Dec 24 2013 *)

%o (PARI) {forstep(i=2,220,2,p=prime(i);if(!isprime(p-i)&&!isprime(p+i),print1(i", ")))}

%Y Cf. A064269, A064402.

%K nonn

%O 1,1

%A _Zak Seidov_, Jan 04 2013

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Last modified August 5 11:48 EDT 2021. Contains 346467 sequences. (Running on oeis4.)