A036912 - OEIS

A036912

Indices of the left-to-right maxima in A057635.

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

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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 A333255 A346729

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