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 A057777 a(n) is the smallest number such that a(n)+1 is a prime and the largest power of 2 which divides it is 2^n. 1

%I

%S 1,2,4,40,16,96,192,640,256,7680,13312,18432,12288,40960,114688,

%T 163840,65536,1179648,786432,5767168,7340032,23068672,104857600,

%U 377487360,754974720,167772160,469762048,2013265920,3489660928,12348030976

%N a(n) is the smallest number such that a(n)+1 is a prime and the largest power of 2 which divides it is 2^n.

%e The 4th term is 40. It is divisible by 8,40+1=41 is prime. Smaller multiples of 8 are not suitable because e.g. albeit 8|16 and 16+1=17 is a prime, but the largest power of 2 which divides 16 is not 8, it is 16. So 16 is not the 3rd, it is the 4th term here.

%Y A000040, A006093.

%K nonn

%O 0,2

%A _Labos Elemer_, Nov 02 2000

%E More terms from Larry Reeves (larryr(AT)acm.org), Nov 03 2000

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Last modified September 27 04:10 EDT 2021. Contains 347673 sequences. (Running on oeis4.)