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Search: id:A131346
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| A131346 |
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a(1)=1. a(n) = a(n-1) + (number of the terms, from among terms a(1) through a(n-1), which are coprime to sum{k=1 to n-1} a(k)). |
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+0
2
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| 1, 2, 4, 7, 8, 10, 12, 14, 16, 18, 20, 21, 30, 43, 47, 62, 70, 80, 89, 95, 115, 123, 145, 152, 162, 172, 179, 206, 234, 263, 270, 276, 286, 298, 307, 333, 341, 376, 404, 439, 449, 489, 507, 537, 557, 602, 635, 655, 690, 725, 749, 787, 812, 838, 863, 905, 920, 941
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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The sum of the first 12 terms of the sequence is 133 = 7*19.
There are 9 terms from among the first 12 terms of the sequence that are coprime to 133 (a(1)=1, a(2)=2, a(3)=4, a(5)=8, a(6)=10, a(7)=12, a(9)=16, a(10)=18, a(11)=20). So a(13)= a(12) + 9 = 30.
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MAPLE
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a[1] := 1; for n from 2 to 60 do ct := 0; for j to n-1 do if gcd(a[j], sum(a[i], i = 1 .. n-1)) = 1 then ct := ct+1 else ct := ct end if end do; a[n] := a[n-1]+ct end do; seq(a[n], n = 1 .. 60) - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jul 17 2007
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CROSSREFS
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Cf. A131347.
Sequence in context: A139212 A127875 A056231 this_sequence A047540 A116478 A047236
Adjacent sequences: A131343 A131344 A131345 this_sequence A131347 A131348 A131349
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Jul 01 2007
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu) and Joshua Zucker (joshua.zucker(AT)stanfordalumni.org), Jul 17 2007
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