A372730 Number of primes <= A005867(n).

0, 0, 1, 4, 15, 92, 757, 8899, 125261, 2232782, 51902553, 1327191561, 41351244491, 1452937916515, 54332144724834, 2246960940148460, 105818707666943651, 5595105626396158784, 308241771351984486729, 18772520681296116861073

Offset

0,4

Links

Table of n, a(n) for n=0..19.

Formula

a(n) = A000720(A005867(n)).

Example

a(3) = 4 because there are 4 primes less than A005867(3) = 8: 2, 3, 5 and 7.

Prog

(Python)
from sympy import prime, primepi
p = 1
l = [0]
for i in range(1, 12):
    p *= (prime(i) - 1)
    l.append(primepi(p))
print(l)
(PARI) A372730(n) = primepi(prod(k=1, n, prime(k)-1)); \\ Antti Karttunen, May 22 2024

Crossrefs

Cf. A000720, A005867, A000849.

Sequence in context: A081011 A008829 A322920 * A332533 A013193 A040025

Adjacent sequences: A372727 A372728 A372729 * A372731 A372732 A372733

Keyword

nonn,more,hard

Author

Alexandre Herrera, May 11 2024

Extensions

a(9)-a(11) from Antti Karttunen, May 22 2024

a(12)-a(16) from Amiram Eldar, May 22 2024

a(17)-a(18) from Chai Wah Wu, Jun 04 2024

a(19) from Chai Wah Wu, Jun 05 2024

Status

approved