A101758 Semiprime tribonacci numbers.

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

Offset

1,1

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.

Formula

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

Mathematica

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

Crossrefs

Cf. A000073, A001358, A101757.

Sequence in context: A221081 A340916 A000320 * A134786 A290225 A190635

Adjacent sequences: A101755 A101756 A101757 * A101759 A101760 A101761

Keyword

nonn

Author

Jonathan Vos Post and Ray Chandler, Dec 26 2004

Status

approved