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A127434 a(0)=1. a(n) = number of earlier terms a(k), 0<=k<=n-1, such that (k+n) is coprime to a(k). 2
1, 1, 2, 3, 3, 4, 4, 6, 4, 6, 7, 6, 7, 9, 8, 10, 10, 10, 9, 12, 10, 12, 15, 11, 14, 14, 14, 16, 17, 15, 16, 20, 16, 19, 21, 19, 20, 23, 19, 22, 25, 23, 27, 26, 25, 27, 31, 29, 28, 33, 29, 29, 37, 33, 34, 37, 33, 35, 37, 38, 36, 42, 38, 41, 43, 36, 41, 46, 42, 43, 47, 44, 46, 49, 42 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..74.

EXAMPLE

(0+9) is coprime to a(0)=1; (1+9) is coprime to a(1)=1; (2+9) is coprime to a(2)=2; (4+9) is coprime to a(4)=3, (6+9) is coprime to a(6)=4; and (8+9) is coprime to a(8)=4. These six cases are the only cases where (k+n) is coprime to a(k), for 0<=k<=8. So a(9) = 6.

MATHEMATICA

f[l_List] := Block[{n = Length[l]}, Append[l, Count[Table[GCD[k + n - 1, l[[k]]], {k, n}], 1]]]; Nest[f, {1}, 75] (*Chandler*)

CROSSREFS

Cf. A127432, A127433.

Sequence in context: A130120 A204892 A164512 * A266475 A205402 A226107

Adjacent sequences:  A127431 A127432 A127433 * A127435 A127436 A127437

KEYWORD

nonn

AUTHOR

Leroy Quet, Jan 14 2007

EXTENSIONS

Extended by Ray Chandler, Jan 22 2007

STATUS

approved

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Last modified January 22 16:36 EST 2018. Contains 298055 sequences.