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 A105935 Indices of Lucas 7-step numbers A104621 which have a nontrivial divisor in common with index. 0
 6, 12, 18, 20, 36, 42, 54, 57, 60, 65, 87, 93, 99, 100, 104, 105, 108 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Wanted: closed-form formula for this as exists for Fibonacci and Lucas numbers. Lucas 7-step numbers also known as heptanacci-Lucas numbers. The prime Lucas 7-step numbers are A105768, their indices being A104622. LINKS FORMULA gcd(a(n), A104621(a(n))) > 1. EXAMPLE gcd(a(n), A104621(6,12,18,36,57,60,87,93,108)) = 3, gcd(a(n), A104621(20,65,100,105)) = 5, gcd(a(n), A104621(42)) = 7, gcd(a(n), A104621(54,99)) = 9, gcd(a(n), A104621(104)) = 13. CROSSREFS Cf. A104621, A105285, A105289. Sequence in context: A088723 A228870 A138939 * A221220 A046411 A160594 Adjacent sequences:  A105932 A105933 A105934 * A105936 A105937 A105938 KEYWORD easy,nonn AUTHOR Jonathan Vos Post, Apr 26 2005 STATUS approved

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