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A143481 a(n) = phi(A143480(n)) where phi(m) = A000010(m). 4
1, 2, 6, 8, 20, 24, 42, 48, 54, 64, 110, 112, 120, 132, 144, 160, 192, 216, 288, 320, 324, 360, 396, 416, 440, 480, 486, 504, 616, 624, 660, 672, 720, 736, 840, 864, 1008, 1044, 1104, 1120, 1200, 1224, 1260, 1280, 1296, 1320, 1380, 1408, 1512, 1560, 1632, 1680 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Previous name was: a(n) is the number of positive integers <= A143480(n) and coprime to A143480(n).

a(n+1) > a(n) for all n.

LINKS

Ivan Neretin and Peter Kagey, Table of n, a(n) for n = 1..10000, first 1000 terms from Ivan Neretin

FORMULA

a(n) = phi(A143480(n)) = A000010(A143480(n)).

MAPLE

A[1]:= 1:

for n from 2 to 100 do

  for k from n by n do

     r:= numtheory:-phi(k);

     if r > A[n-1] then

        A[n]:= r;

        break

     fi

  od:

od:

seq(A[i], i=1..100); # Robert Israel, Sep 04 2015

MATHEMATICA

a = b = {1}; Do[k = 1; While[(r = EulerPhi[nxt = k*n]) <= b[[-1]], k++]; AppendTo[a, nxt]; AppendTo[b, r], {n, 2, 52}]; b (* Ivan Neretin, May 25 2015 *)

CROSSREFS

Cf. A143480.

A143483 is an analogous sequence with A143482 as the referenced sequence.

Sequence in context: A135616 A069553 A275826 * A093968 A064713 A162213

Adjacent sequences:  A143478 A143479 A143480 * A143482 A143483 A143484

KEYWORD

nonn

AUTHOR

Leroy Quet, Aug 19 2008

EXTENSIONS

Extended by Ray Chandler, Nov 09 2008

Name changed by Peter Kagey, Sep 03 2015

STATUS

approved

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Last modified August 12 11:42 EDT 2020. Contains 336439 sequences. (Running on oeis4.)