A123711 Indices n such that A123709(n) = 8 = number of nonzero terms in row n of triangle A123706.

12, 18, 20, 24, 28, 36, 40, 44, 45, 48, 50, 52, 54, 56, 63, 68, 72, 75, 76, 80, 88, 92, 96, 98, 99, 100, 104, 108, 112, 116, 117, 124, 135, 136, 144, 147, 148, 152, 153, 160, 162, 164, 171, 172, 175, 176, 184, 188, 189, 192, 196, 200, 207, 208, 212, 216, 224, 225

Offset

1,1

Comments

Triangle A123706 is the matrix inverse of triangle A010766, where A010766(n,k) = [n/k].

It appears that this equals A200511, numbers of the form p^k q^m with k,m >= 1, k+m > 2 and p, q prime. - M. F. Hasler, Feb 12 2012

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Mathematica

Moebius[i_, j_] := If[Divisible[i, j], MoebiusMu[i/j], 0]; A123709[n_] :=
Length[Select[Table[Moebius[n, j] - Moebius[n, j + 1], {j, 1, n}], # != 0 &]]; Select[Range[500], A123709[#] == 8 &] (* G. C. Greubel, Apr 22 2017 *)

Prog

(PARI)

Crossrefs

Cf. A123706, A123709, A123710, A123712; A010766.

Sequence in context: A102467 A342973 A126706 * A200511 A370409 A363101

Adjacent sequences: A123708 A123709 A123710 * A123712 A123713 A123714

Keyword

nonn

Author

Paul D. Hanna, Oct 09 2006

Status

approved