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a(n) is the largest prime p < 2^n such that p + 2^n is also prime.
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%I #21 Feb 20 2017 00:30:36

%S 3,5,13,29,43,113,223,509,907,2003,4051,8171,16333,32603,65437,130649,

%T 262027,524261,1048507,2097047,4194277,8388209,16776481,33554201,

%U 67108753,134217401,268435273,536869631,1073741719,2147483549,4294966477,8589934307,17179868383

%N a(n) is the largest prime p < 2^n such that p + 2^n is also prime.

%e 13 + 16 (2^4) = 29 (prime).

%e 29 + 32 (2^5) = 61 (prime).

%e 43 + 64 (2^6) = 107 (prime).

%Y Cf. A000040, A000079.

%K nonn

%O 2,1

%A _Emre APARI_, Feb 18 2017