A101758 Semiprime tribonacci numbers.

4, 274, 10609, 23837527729, 80641778674, 3122171529233, 408933139743937, 98513851446415969, 7015254043203144209, 1690006574433492223897, 120346786571258131649185, 2533271375725618104752561

Offset: 1

Author

Jonathan Vos Post and Ray Chandler, Dec 26 2004

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..28
• Eric Weisstein's World of Mathematics, Semiprime.
• Eric Weisstein's World of Mathematics, Tribonacci Number.

Crossrefs

Cf. A000073, A001358, A101757.

Programs

Mathematica

Select[LinearRecurrence[{1,1,1},{0,1,1},150],PrimeOmega[#]==2&] (* Harvey P. Dale, Oct 16 2012 *)

Formula

a(n) = A000073(A101757(n)).