A366583 a(2) = a(3) = 1; for n >3, a(n) = smallest prime factor of n-th Tribonacci number.

1, 1, 2, 2, 7, 13, 2, 2, 3, 149, 2, 2, 3, 5, 2, 2, 103, 13, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 23, 5, 2, 2, 3, 103, 2, 2, 7, 3, 2, 2, 167, 11, 2, 2, 5, 3, 2, 2, 199, 5, 2, 2, 7, 163, 2, 2, 29531, 5, 2, 2, 3, 5, 2, 2, 3, 199, 2, 2, 7, 19, 2, 2, 1259, 3, 2, 2, 3, 3

Offset: 2

Author

Tyler Busby, Oct 13 2023

Keywords

• nonn

Examples

			For n=24: A000073(24) = 2*2*2*51343, so a(24)=2.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 2..365

Crossrefs

Cf. A000073, A231575, A101757.

Programs

Mathematica

FactorInteger[#][[1, 1]] & /@ LinearRecurrence[{1, 1, 1}, {1, 1, 2}, 78] (* Amiram Eldar, Oct 23 2023 *)

Formula

a(n) = A020639(A000073(n)).