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 A382481 #17 Mar 30 2025 09:53:30 %S A382481 0,2,54,23000,203280221,33483379603407,96601075195075186855 %N A382481 a(n) is the number of primes less than 4^(n^2). %C A382481 Thue's proof, that there exist infinitely many primes, shows also that n+1 is a lower bound for a(n) (see Ribenboim, 2004). %D A382481 Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See pp. 9-10. %H A382481 a(n) = pi(4^(n^2)). %H A382481 a(n) = A007053(2*n^2). - _Amiram Eldar_, Mar 29 2025 %t A382481 a[n_]:=PrimePi[4^(n^2)]; Array[a,6,0] %o A382481 (Python) %o A382481 from sympy import primepi %o A382481 def A382481(n): return primepi(1<<(n**2<<1)) # _Chai Wah Wu_, Mar 29 2025 %Y A382481 Cf. A000290, A000302, A000720, A007053, A060757. %K A382481 nonn,hard,more %O A382481 0,2 %A A382481 _Stefano Spezia_, Mar 28 2025