Cullen Number

A Cullen number is a number of the form

The first few are 3, 9, 25, 65, 161, 385, ... (OEIS A002064).

Cullen numbers are divisible by if is a prime of the form .

The first few prime Cullen numbers are numbers 3, 393050634124102232869567034555427371542904833, ... (OEIS A050920), corresponding to , 141, 4713, 5795, 6611, 18496, 32292, 32469, 59656, 90825, 262419, 361275, 481899, 1354828, 6328548, 6679881, ... (OEIS A005849; Caldwell). As of Nov. 2015, it is known that there are no other Cullen primes for (PrimeGrid).

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