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A159475
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a(1) = 1; for n >= 1, a(n) is the smallest number m > n such that gcd(n,m) > 1.
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4
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1, 4, 6, 6, 10, 8, 14, 10, 12, 12, 22, 14, 26, 16, 18, 18, 34, 20, 38, 22, 24, 24, 46, 26, 30, 28, 30, 30, 58, 32, 62, 34, 36, 36, 40, 38, 74, 40, 42, 42, 82, 44, 86, 46, 48, 48, 94, 50, 56, 52, 54, 54, 106, 56, 60, 58, 60, 60, 118, 62, 122, 64, 66, 66, 70, 68, 134, 70, 72, 72
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OFFSET
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1,2
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COMMENTS
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Essentially the same as A061228. [R. J. Mathar, Apr 16 2009]
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..10000
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FORMULA
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If n = Product (p_i^e_i), where p_1 < p_2 < ... < p_k, a(n) = n + p_1. For p = primes (A000040), a(p) = 2*p.
a(n) = n + A020639(n), for n > 1. - Michel Marcus, Dec 02 2018
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MATHEMATICA
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f[n_]:= n + FactorInteger[n][[1, 1]]; Join[{1}, Array[f, 70, 2]] (* Vincenzo Librandi, Dec 02 2018 *)
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PROG
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(PARI) a(n) = if (n==1, 1, n+factor(n)[1, 1]); \\ Michel Marcus, Dec 02 2018
(MAGMA) [1] cat [n + PrimeDivisors(n)[1]: n in [2..100]]; // Vincenzo Librandi, Dec 02 2018
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CROSSREFS
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Cf. A000040, A020639, A061228.
Sequence in context: A160995 A215454 A155750 * A098350 A276269 A163173
Adjacent sequences: A159472 A159473 A159474 * A159476 A159477 A159478
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KEYWORD
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nonn
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AUTHOR
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Jaroslav Krizek, Apr 13 2009
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EXTENSIONS
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More terms from Michel Marcus, Dec 02 2018
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STATUS
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approved
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