A379810 Composite numbers in A381019 which are immediately followed by another composite number, in order of their appearance.

15, 46, 104, 305, 261, 1691, 380, 406, 508, 1175, 3281, 7729, 2827, 10877, 6289, 13289, 1737, 4829, 2945, 3205, 9673, 1940, 21253, 1970, 31921, 21127, 34861, 5457, 22219, 120983, 99893, 110843, 148613, 105029, 164107, 12905, 89279, 15245, 195617, 79909, 89827

Offset: 1

Author

N. J. A. Sloane, Feb 15 2025

Keywords

• nonn

Comments

Conjecture: For any k >= 1, A381019 contains k consecutive composite terms.

When is the first instance of three consecutive composite terms?

Crossrefs

Cf. A381019, A381120.

Formula

a(n) = A381019(A381120(n)).

Extensions

a(6)-a(8) from Michael De Vlieger, Feb 15 2025

More terms from Jinyuan Wang, Feb 23 2025