A374105 Numbers k such that (9^k + 3^k + 1)/13 is prime.
2, 5, 7, 11, 541, 1583, 2713, 2963, 13831, 22349, 22669, 23833, 57287
Offset: 1
Examples
5 is a term because (9^5 + 3^5 + 1)/13 = 4561 is prime.
Programs
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PARI
isok(k)={k%3 && ispseudoprime((9^k + 3^k + 1)/13)} { for(k=1, 2000, if(isok(k), print1(k, ", "))) }
Extensions
a(13) confirmed by Michael S. Branicky, Sep 13 2024
Comments