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A159475
a(1) = 1; for n >= 1, a(n) is the smallest number m > n such that gcd(n,m) > 1.
4
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
OFFSET
1,2
COMMENTS
Essentially the same as A061228. [R. J. Mathar, Apr 16 2009]
LINKS
FORMULA
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
MATHEMATICA
f[n_]:= n + FactorInteger[n][[1, 1]]; Join[{1}, Array[f, 70, 2]] (* Vincenzo Librandi, Dec 02 2018 *)
PROG
(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
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Apr 13 2009
EXTENSIONS
More terms from Michel Marcus, Dec 02 2018
STATUS
approved