A285525 The indices that mark the beginning of four consecutive equal terms in A285524.

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

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-François 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