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Search: id:A105289
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| A105289 |
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Indices of Lucas 5-step numbers A074048 which have a nontrivial divisor in common with index. |
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+0
2
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| 6, 12, 18, 20, 21, 33, 36, 48, 51, 54, 55, 60, 75, 78, 87, 99, 100
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Extension by T. D. Noe (noe(AT)sspectra.com). Wanted: closed-form formula for this as exists for Fibonacci and Lucas numbers. See also A105764 Indices of prime Lucas 5-step numbers.
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FORMULA
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gcd(a(n), A074048(a(n))) > 1.
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EXAMPLE
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gcd(6, A074048(6)) = gcd(6,57) = 3,
gcd(20, A074048(20)) = gcd(20,743775) = 5.
gcd(21, A074048(21)) = gcd(21,1462223) = 7.
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CROSSREFS
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Cf. A074048, A104714, A105764.
Sequence in context: A023495 A037363 A049094 this_sequence A051774 A119357 A097216
Adjacent sequences: A105286 A105287 A105288 this_sequence A105290 A105291 A105292
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Apr 25 2005
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