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A167170
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a(6) = 14, for n >= 7, a(n) = a(n-1) + gcd(n, a(n-1)).
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8
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14, 21, 22, 23, 24, 25, 26, 39, 40, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 87, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 177, 180, 181, 182, 189, 190, 195
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OFFSET
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6,1
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COMMENTS
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For every n >= 7, a(n) - a(n-1) is 1 or prime. This Rowland-like "generator of primes" is different from A106108 (see comment to A167168).
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LINKS
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MAPLE
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A167170 := proc(n) option remember; if n = 6 then 14; else procname(n-1)+igcd(n, procname(n-1)) ; end if; end proc: seq(A167170(i), i=6..80) ; # R. J. Mathar, Oct 30 2010
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MATHEMATICA
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RecurrenceTable[{a[n] == a[n - 1] + GCD[n, a[n - 1]], a[6] == 14}, a, {n, 6, 100}] (* G. C. Greubel, Jun 04 2016 *)
nxt[{n_, a_}]:={n+1, a+GCD[a, n+1]}; NestList[nxt, {6, 14}, 60][[All, 2]] (* Harvey P. Dale, Nov 03 2019 *)
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PROG
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(PARI) first(n)=my(v=vector(n-5)); v[1]=14; for(k=7, n, v[k-5]=v[k-6]+gcd(k, v[k-6])); v \\ Charles R Greathouse IV, Aug 22 2017
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CROSSREFS
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Cf. A167168, A106108, A132199, A167054, A167053, A166944, A166945, A116533, A163961, A163963, A084662, A084663, A134162, A135506, A135508, A118679, A120293.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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