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 A191699 #14 Apr 13 2025 14:57:59 %S A191699 3,4,6,9,31,187,632,2972 %N A191699 Numbers k such that k*(k-1)^k - (k-1)*k^(k-1) - 1 is prime. %C A191699 a(9) > 20000. - _Michael S. Branicky_, Apr 13 2025 %e A191699 a(1)=3 because 3*2^3-2*3^2-1=5 is prime, a(2)=4 because 4*3^4-3*4^3-1=131 is prime, a(3)=6 because 6*5^6-5*6^5-1=54869 is prime, a(4)=9 because 9*8^9-8*9^8-1=863585783 is prime. %o A191699 (Python) %o A191699 from sympy import isprime %o A191699 def afind(limit, startk=1): %o A191699 for k in range(startk, limit+1): %o A191699 if isprime(k*(k-1)**k - (k-1)*k**(k-1) - 1): %o A191699 print(k, end=", ") %o A191699 afind(200) # _Michael S. Branicky_, Jan 10 2022 %Y A191699 Cf. A191409 (associated primes). %K A191699 nonn,hard,more %O A191699 1,1 %A A191699 _Juri-Stepan Gerasimov_, Jun 12 2011 %E A191699 a(8) from _Michael S. Branicky_, Jan 10 2022