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, 2, 4, 40, 16, 96, 192, 640, 256, 7680, 13312, 18432, 12288, 40960, 114688, 163840, 65536, 1179648, 786432, 5767168, 7340032, 23068672, 104857600, 377487360, 754974720, 167772160, 469762048, 2013265920, 3489660928, 12348030976

Offset

0,2

Links

Table of n, a(n) for n=0..29.

Formula

a(n) = A057775(n) - 1. - Sean A. Irvine, Jun 27 2022

Example

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.

Crossrefs

Cf. A000040, A006093, A057775, A057776.

Sequence in context: A106127 A018992 A098625 * A139735 A184952 A098337

Adjacent sequences: A057774 A057775 A057776 * A057778 A057779 A057780

Keyword

nonn

Author

Labos Elemer, Nov 02 2000

Extensions

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

Status

approved