Is there a reason POTUS was quoting Hilbert Primes at the rally last night?

In number theory a Hilbert number is a positive integer of the form 4n + 1. The Hilbert numbers were named after David Hilbert. The sequence of Hilbert numbers begins 1, 5, 9, 13, 17, .. A Hilbert prime is a Hilbert number that is not divisible by a smaller Hilbert number (other than 1). The sequence of Hilbert primes begins

5, 9, 13, 17, 21, 29, 33, 37, 41, 49, ..

en.wikipedia.org/wiki/Hilbert_number

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