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Search: id:A118418
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| A118418 |
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Relative-prime-indexed recurrence. |
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+0
2
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| 1, 1, 2, 4, 8, 9, 25, 36, 75, 103, 264, 298, 826, 1176, 2333
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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For prime p, a(p) = SUM[i=1..p-1] a(i). a(3) = 2, a(10) = 103, and a(15) = 2333 are primes. See also: A118314 Divisor-indexed recurrence.
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FORMULA
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a(1) = a(2) = 1; a(n) = SUM[i such that GCD(i,n) = 1] a(i). a(n) = SUM[k relatively prime to n and k<n] a(k).
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EXAMPLE
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a(6) = 9 because a(1) + a(5) = 1 + 8 = 9, where only 1 and 5 are less than and relatively prime to 6.
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CROSSREFS
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Cf. A118314.
Sequence in context: A046685 A140141 A088274 this_sequence A074810 A028984 A043706
Adjacent sequences: A118415 A118416 A118417 this_sequence A118419 A118420 A118421
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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), May 16 2006
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