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 A104623 Indices of semiprime (A001358) values of Heptanacci-Lucas numbers A104621. 2
 4, 8, 9, 11, 12, 14, 15, 16, 22, 23, 32, 34, 37, 41, 42, 50, 52, 57, 58, 66, 69, 76, 77, 81, 90 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS 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. REFERENCES Mario Catalani, "Polymatrix and Generalized Polynacci Numbers", arXiv:math.CO/0210201 v1, 2002 LINKS Eric Weisstein's World of Mathematics, Semiprime. EXAMPLE A104621(4) = 15 = 3 * 5, A104621(8) = 247 = 13 * 19, A104621(9) = 493 = 17 * 29, A104621(11) = 1959 = 3 * 653, A104621(12) = 3903 = 3 * 1301, A104621(14) = 15487 = 17 * 911, CROSSREFS Cf. A001358. Sequence in context: A118715 A175839 A226085 * A228653 A158758 A229004 Adjacent sequences:  A104620 A104621 A104622 * A104624 A104625 A104626 KEYWORD nonn AUTHOR Jonathan Vos Post, Mar 17 2005 STATUS approved

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