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

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

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

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

Crossrefs

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

Programs

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 *)

Formula

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

Extensions

More precise definition from Max Alekseyev, Nov 07 2007

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