A379566 Number of n-digit numbers that have exactly 3 divisors.

2, 2, 7, 14, 40, 103, 278, 783, 2172, 6191, 17701, 51205, 149149, 436932, 1287378, 3809498, 11321211, 33764868, 101029398, 303175579, 912147300, 2750855002, 8313825647, 25176031558, 76375623757, 232082001064, 706304629714, 2152571584249, 6568923555719

Offset: 1

Author

Seiichi Manyama, Dec 26 2024

Keywords

• nonn
• base

Crossrefs

Column k=3 of A284398.

Cf. A001248, A006880, A122121.

Formula

a(n) = A122121(n) - A122121(n-1).

Extensions

a(18)-a(29) from Seiichi Manyama using A122121 data, Dec 26 2024