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 A372730 #29 Jun 05 2024 21:52:44 %S A372730 0,0,1,4,15,92,757,8899,125261,2232782,51902553,1327191561, %T A372730 41351244491,1452937916515,54332144724834,2246960940148460, %U A372730 105818707666943651,5595105626396158784,308241771351984486729,18772520681296116861073 %N A372730 Number of primes <= A005867(n). %F A372730 a(n) = A000720(A005867(n)). %e A372730 a(3) = 4 because there are 4 primes less than A005867(3) = 8: 2, 3, 5 and 7. %o A372730 (Python) %o A372730 from sympy import prime,primepi %o A372730 p = 1 %o A372730 l = [0] %o A372730 for i in range(1,12): %o A372730 p *= (prime(i) - 1) %o A372730 l.append(primepi(p)) %o A372730 print(l) %o A372730 (PARI) A372730(n) = primepi(prod(k=1, n, prime(k)-1)); \\ _Antti Karttunen_, May 22 2024 %Y A372730 Cf. A000720, A005867, A000849. %K A372730 nonn,more,hard %O A372730 0,4 %A A372730 _Alexandre Herrera_, May 11 2024 %E A372730 a(9)-a(11) from _Antti Karttunen_, May 22 2024 %E A372730 a(12)-a(16) from _Amiram Eldar_, May 22 2024 %E A372730 a(17)-a(18) from _Chai Wah Wu_, Jun 04 2024 %E A372730 a(19) from _Chai Wah Wu_, Jun 05 2024