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A036912 Indices of the left-to-right maxima in A057635. 8
1, 2, 4, 6, 8, 12, 16, 20, 24, 32, 36, 40, 48, 64, 72, 80, 96, 120, 128, 144, 160, 176, 192, 224, 240, 288, 320, 336, 384, 432, 480, 576, 672, 720, 768, 864, 960, 1056, 1152, 1280, 1296, 1344, 1440, 1536, 1680, 1728, 1920, 2112, 2208, 2304, 2400, 2592, 2688 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A number m belongs to this sequence iff A057635(k) < A057635(m) for all k<m.

Indices of records in A057635(n), the maximal m with phi(m)=n.

The Alekseyev link in A131883 establishes the following explicit relationship between A131883, A036912 and A057635. Namely, for t belonging to A036912, we have t=A131883(A057635(t)-1). In other words, A036912(n) = A131883(A057635(A036912(n))-1) for all n.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..5000

FORMULA

a(n) = A000010(A036913(n)). - Max Alekseyev, Nov 07 2007

MATHEMATICA

Block[{nn = 10^6, s, t, u}, s = PositionIndex@ Array[EulerPhi, nn]; t = ConstantArray[0, nn]; u = Take[ReplacePart[t, Map[# -> Last@ Lookup[s, #] &, Keys@ s]], 10^(Log10[nn] - 2)]; Map[FirstPosition[u, #][[1]] &, Union@ FoldList[Max, u]]] (* Michael De Vlieger, Oct 24 2017 *)

CROSSREFS

Cf. A057635, A000010, A006511, A036913, A132154, A131883.

Sequence in context: A246663 A182568 A064522 * A306371 A097921 A185976

Adjacent sequences:  A036909 A036910 A036911 * A036913 A036914 A036915

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

More precise definition from Max Alekseyev, Nov 07 2007

STATUS

approved

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Last modified September 15 18:22 EDT 2019. Contains 327082 sequences. (Running on oeis4.)