A133439 - OEIS

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A133439

a(1)=1; a(n) = Sum_{1<=k<=n, gcd(k,n)=1} a(floor(sqrt(k))).

1, 1, 2, 2, 4, 2, 6, 4, 6, 5, 12, 5, 16, 9, 11, 12, 24, 9, 28, 13, 19, 16, 36, 13, 33, 22, 34, 25, 56, 16, 64, 36, 46, 38, 56, 29, 86, 44, 56, 37, 94, 28, 98, 46, 55, 52, 106, 37, 95, 49, 80, 64, 134, 49, 107, 67, 106, 82, 170, 46, 182, 94, 111, 104, 149, 63, 212, 104, 146, 78

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..70.

EXAMPLE

The positive integers that are <12 and are coprime to 12 are 1,5,7,11. The floors of the square roots of these are 1,2,2,3. So a(12) = a(1) + a(2) + a(2) + a(3) = 1 + 1 + 1 + 2 = 5.

MATHEMATICA

a = {1}; Do[s = 0; For[j = 1, j < n, j++, If[GCD[j, n] == 1, s = s + a[[Floor[Sqrt[j]]]]]]; AppendTo[a, s], {n, 2, 80}]; a (* Stefan Steinerberger, Dec 19 2007 *)

CROSSREFS

Sequence in context: A122646 A028496 A063428 * A234649 A072300 A210359

Adjacent sequences: A133436 A133437 A133438 * A133440 A133441 A133442

KEYWORD

nonn

AUTHOR

Leroy Quet, Nov 26 2007

EXTENSIONS

More terms from Stefan Steinerberger, Dec 19 2007

STATUS

approved