This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A246121 #25 Apr 03 2023 10:36:13 %S A246121 2,3,88,28,688,7003,1925 %N A246121 Least k such that k^(6^n)*(k^(6^n) - 1) + 1 is prime. %C A246121 Numbers of the form k^m*(k^m - 1) + 1 with m > 0, k > 1 may be primes only if m is 3-smooth, because these numbers are Phi(6,k^m) and cyclotomic factorizations apply to any prime divisors > 3. This sequence is a subset of A205506 with only m=6^n. %C A246121 Numbers of this form are Generalized unique primes. a(6) generates a 306477-digit prime. %H A246121 C. Caldwell, <a href="https://t5k.org/top20/page.php?id=44">Generalized unique primes</a> %F A246121 a(n) = A085398(6^(n+1)). - _Jinyuan Wang_, Jan 01 2023 %e A246121 When k = 88, k^72 - k^36 + 1 is prime. Since this isn't prime for k < 88, a(2) = 88. %o A246121 (PARI) a(n)=k=1; while(!ispseudoprime(k^(6^n)*(k^(6^n)-1)+1), k++); k %o A246121 n=0; while(n<100, print1(a(n), ", "); n++) %Y A246121 Cf. A056993, A085398, A101406, A153436, A153438, A205506, A246119, A246120. %K A246121 nonn,more,hard %O A246121 0,1 %A A246121 _Serge Batalov_, Aug 14 2014 %E A246121 a(6) from _Serge Batalov_, Aug 15 2014