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A132801 a(0)=1; a(n) = Sum_{1<=k<=n, GCD(k,n)=1} a(floor(k/2)), where the sum is over those positive integers which are <= n and are coprime to n. 0
1, 1, 1, 2, 2, 4, 2, 7, 5, 8, 6, 17, 8, 23, 11, 20, 20, 44, 15, 57, 25, 40, 35, 94, 40, 101, 62, 114, 79, 184, 50, 215, 118, 155, 133, 247, 123, 378, 189, 311, 194, 532, 117, 597, 295, 373, 337, 801, 297, 825, 393, 741, 530, 1239, 399, 1088, 673, 1042, 833, 1871, 530 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..60.

EXAMPLE

The positive integers which are <= 12 and are coprime to 12 are 1,5,7,11. Dividing each of these by 2 and rounding down, we get 0,2,3,5. So a(12) = a(0)+a(2)+a(3)+a(5) = 1+1+2+4 = 8.

MATHEMATICA

a = {1}; For[n = 1, n < 70, n++, s = 0; b = Select[Range[n], GCD[n, # ] == 1 &]; For[j = 1, j < Length[b] + 1, j++, s = s + a[[Floor[b[[j]]/2] + 1]]]; AppendTo[a, s]]; a (* Stefan Steinerberger, Nov 20 2007 *)

CROSSREFS

Sequence in context: A275870 A003980 A286369 * A270366 A072478 A190014

Adjacent sequences:  A132798 A132799 A132800 * A132802 A132803 A132804

KEYWORD

nonn

AUTHOR

Leroy Quet, Nov 17 2007

EXTENSIONS

More terms from Stefan Steinerberger, Nov 20 2007

STATUS

approved

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Last modified February 21 14:40 EST 2018. Contains 299414 sequences. (Running on oeis4.)