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 A381815 #25 Apr 15 2025 07:39:58 %S A381815 3,2,2,2,138,24,695,107,250,404,4657,2185,27931 %N A381815 Smallest k>1 such that 10*k^(3*2^n)+1 is prime. %e A381815 a(0) = 3, because 10*3^(3*2^0)+1 equals 271 which is prime. %e A381815 a(1) = 2, because 10*2^(3*2^1)+1 equals 641 which is prime. %o A381815 (Python) %o A381815 from sympy import isprime %o A381815 from itertools import count %o A381815 def a(n): return next(k for k in count(2) if isprime(k**(3*(2**n)) * 10 + 1)) %Y A381815 Cf. A007283, A002254, A089319. %Y A381815 Cf. A381793. %K A381815 nonn,base,more,hard %O A381815 0,1 %A A381815 _Jakub Buczak_, Mar 07 2025 %E A381815 a(10)-a(11) from _Michael S. Branicky_, Mar 07 2025 %E A381815 a(12) from _Georg Grasegger_, Apr 15 2025