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Search: id:A077224
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| A077224 |
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a(1) = 1; for n>1, a(n) = smallest number > a(n-1) such that a(n) + a(k) is square-free for k = 1 to n-1. |
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4
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| 1, 2, 4, 9, 13, 29, 33, 101, 105, 109, 157, 177, 253, 289, 301, 353, 409, 429, 465, 501, 533, 553, 589, 609, 681, 753, 877, 933, 965, 1153, 1477, 1905, 1977, 2101, 2125, 2229, 2305, 2405, 2605, 2657, 2801, 2913, 3305, 3381, 3489, 3565, 3777, 3781, 3881, 4029
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Or, sum of any two terms is a squarefree number.
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FORMULA
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It can easily be proved that a(n) == 1 mod 4 for all n >3.
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EXAMPLE
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13 is a member as 13 + 1, 13 + 2, 13 + 4, 13 + 9 are all square-free.
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CROSSREFS
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Cf. A085902.
Sequence in context: A049793 A090942 A085901 this_sequence A059447 A078671 A119637
Adjacent sequences: A077221 A077222 A077223 this_sequence A077225 A077226 A077227
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 03 2002
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EXTENSIONS
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Edited by Sam Alexander (amnalexander(AT)yahoo.com), Dec 12 2003
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