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A126881 a(1)=1, a(2)=2. a(n) is the a(n-1)th integer from among those positive integers coprime to a(n-2). 1
1, 2, 2, 3, 5, 7, 8, 9, 17, 25, 26, 32, 69, 137, 214, 215, 433, 553, 554, 654, 1311, 3967, 6565, 6566, 8979, 21267, 33151, 53216, 53217, 106497, 161963, 242965, 244832, 306046, 714759, 1579093, 2396450, 2420102, 7278679, 14557369, 14778071 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..41.

EXAMPLE

a(4)=3, a(5)=5. So a(6) is the 5th positive integer which is coprime to 3. 3 is coprime to 1,2,4,5,7,8,10,11,... So a(6) is the 5th of these, which is 7.

MATHEMATICA

f[m_, n_] := Block[{k = 0, c = n}, While[c > 0, k++; While[GCD[k, m] > 1, k++ ]; c--; ]; k]; g[l_] := Append[l, f[l[[ -2]], l[[ -1]]]]; Nest[g, {1, 2}, 40] (* Ray Chandler, Dec 31 2006 *)

CROSSREFS

Cf. A126882.

Sequence in context: A178880 A079953 A133393 * A290273 A125505 A061565

Adjacent sequences:  A126878 A126879 A126880 * A126882 A126883 A126884

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 29 2006

EXTENSIONS

Extended by Ray Chandler, Dec 31 2006

STATUS

approved

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Last modified December 5 13:26 EST 2019. Contains 329751 sequences. (Running on oeis4.)