This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A101758 #17 Feb 16 2025 08:32:55
%S A101758 4,274,10609,23837527729,80641778674,3122171529233,408933139743937,
%T A101758 98513851446415969,7015254043203144209,1690006574433492223897,
%U A101758 120346786571258131649185,2533271375725618104752561
%N A101758 Semiprime tribonacci numbers.
%H A101758 Amiram Eldar, <a href="/A101758/b101758.txt">Table of n, a(n) for n = 1..28</a>
%H A101758 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Semiprime.html">Semiprime</a>.
%H A101758 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TribonacciNumber.html">Tribonacci Number</a>.
%F A101758 a(n) = A000073(A101757(n)).
%t A101758 Select[LinearRecurrence[{1,1,1},{0,1,1},150],PrimeOmega[#]==2&] (* _Harvey P. Dale_, Oct 16 2012 *)
%Y A101758 Cf. A000073, A001358, A101757.
%K A101758 nonn
%O A101758 1,1
%A A101758 _Jonathan Vos Post_ and _Ray Chandler_, Dec 26 2004