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A285525 The indices that mark the beginning of four consecutive equal terms in A285524. 2
13, 38, 63, 85, 110, 135, 160, 185, 210, 232, 257, 282, 307, 332, 354, 379, 404, 429, 454, 479, 501, 526, 551, 576, 601, 626, 648, 673, 698, 723, 748, 770, 795, 820, 845, 870, 895, 917, 942, 967, 992, 1017, 1042, 1064, 1089, 1114, 1139, 1164, 1186, 1211, 1236, 1261 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..52.

Robert Davis, Sarah A. Nelson, T. Kyle Petersen, Bridget E. Tenner, The pinnacle set of a permutation, arXiv:1704.05494 [math.CO], 2017.

MATHEMATICA

b[n_] := b[n] = MaximalBy[Table[{d, d! (d+1)! 2^(n - 2d - 1) StirlingS2[n - d, d + 1]}, {d, 1, n/2}], Last][[All, 1]] // Min;

A285524 = Table[b[n], {n, 4, 1000}];

Position[If[Length[#] == 4, Join[{0}, Rest[#]], #]& /@ Split[A285524] // Flatten, 0] + 3 // Flatten (* Jean-Fran├žois Alcover, Feb 23 2019 *)

PROG

(PARI) half(n) = if (n % 2, n\2, n/2 - 1);

a285524(n) = {v = vector(half(n), d, d!*(d + 1)!*(2^(n-2*d-1)*stirling(n-d, d+1, 2))); w = vecsort(v, , 1); w[#w]; }

lista(nn) = {v = vector(nn, n, a285524(n+3)); for (k=1, #v-4, if ((v[k] == v[k+1]) && (v[k] == v[k+2]) && (v[k] == v[k+3]), print1(k+3, ", ")); ); }

CROSSREFS

Cf. A285524, A285526.

Sequence in context: A244185 A044090 A044471 * A209991 A299055 A158647

Adjacent sequences:  A285522 A285523 A285524 * A285526 A285527 A285528

KEYWORD

nonn

AUTHOR

Michel Marcus, Apr 20 2017

EXTENSIONS

More terms from Jinyuan Wang, Feb 10 2020

STATUS

approved

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Last modified March 7 01:27 EST 2021. Contains 341859 sequences. (Running on oeis4.)