%I A104623
%S A104623 4,8,9,11,12,14,15,16,22,23,32,34,37,41,42,50,52,57,58,66,69,76,77,81,
%T A104623 90
%N A104623 Indices of semiprime (A001358) values of Heptanacci-Lucas numbers A104621.
%C A104623 The 7th-order linear recurrence A104622 (heptanacci-Lucas numbers) is 
               a generalization of the Lucas sequence A000032. T. D. Noe and I have 
               noted that the heptanacci-Lucas numbers have many more primes than 
               the corresponding heptanacci (see A104414) which he found has only 
               the first 3 primes that I identified through the first 5000 values, 
               whereas these heptanacci-Lucas numbers have 17 primes among the first 
               100 values. For primes in Heptanacci-Lucas numbers, see A104622.
%D A104623 Mario Catalani, "Polymatrix and Generalized Polynacci Numbers", arXiv:math.CO/
               0210201 v1, 2002
%H A104623 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Semiprime.html">Semiprime</a>.
%e A104623 A104621(4) = 15 = 3 * 5,
%e A104623 A104621(8) = 247 = 13 * 19,
%e A104623 A104621(9) = 493 = 17 * 29,
%e A104623 A104621(11) = 1959 = 3 * 653,
%e A104623 A104621(12) = 3903 = 3 * 1301,
%e A104623 A104621(14) = 15487 = 17 * 911,
%Y A104623 Cf. A001358.
%Y A104623 Sequence in context: A073042 A094349 A118715 this_sequence A158758 A078137 
               A010453
%Y A104623 Adjacent sequences: A104620 A104621 A104622 this_sequence A104624 A104625 
               A104626
%K A104623 nonn
%O A104623 0,1
%A A104623 Jonathan Vos Post (jvospost3(AT)gmail.com), Mar 17 2005