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Search: id:A036456
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| A036456 |
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If the number of divisor-function is applied 4 times for any of a[ n ], then the result is the fixed point, i.e. 2. |
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2
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| 12, 18, 20, 24, 28, 30, 32, 40, 42, 44, 45, 48, 50, 52, 54, 56, 63, 66, 68, 70, 75, 76, 78, 80, 88, 92, 98, 99, 102, 104, 105, 110, 112, 114, 116, 117, 124, 128, 130, 135, 136, 138, 144, 147, 148, 152, 153, 154, 162, 164, 165, 170, 171, 172, 174, 175, 176, 182
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Similar to but different from A007624. Terms like 60,72,84,90,96,108,126, etc. are not present here.
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FORMULA
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Nest[ d, a[ n ], 4 ] = 2 for all n or d[ d[ d[ d[ a[ n ] ] ] ] ]=2
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EXAMPLE
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a[ 3 ]=20 and a[ 17 ]=63; for both a, d[ a ]=6 and d[ d[ a ] ]=4, the 3rd iterates are 3 and the equilibrium value, i.e. 2 appears as 4th iterates.
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CROSSREFS
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Cf. A007624, A036450, A046452, A036453, A036455.
Adjacent sequences: A036453 A036454 A036455 this_sequence A036457 A036458 A036459
Sequence in context: A025491 A091196 A007624 this_sequence A102467 A126706 A123711
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu)
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