The $n$-th Cullen number is equal to $n \times 2^n +1$.
Cullen numbers have been studied because they are seldom prime. They are prime for n = 1, 141, 4713, 5795, 6611, 18496, 32292, 32469, 59656, 90825, 262419,...
The first Cullen numbers are 1, 3, 9, 25, 65, 161, 385, 897, 2049, 4609, 10241, 22529, 49153, 106497, 229377, 491521, 1048577
Pictorial representation of remainders (mod 2, 3, ...,11) frequency. For a table of values and more details click here
A graph displaying how many Cullen numbers are multiples of the primes p from 2 to 71. In black the ideal line 1/p.
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