A123712 Indices n such that 16 = A123709(n) = number of nonzero terms in row n of triangle A123706.

60, 84, 90, 120, 126, 132, 140, 150, 156, 168, 180, 198, 204, 220, 228, 234, 240, 252, 260, 264, 270, 276, 280, 294, 300, 306, 308, 312, 315, 336, 340, 342, 348, 350, 360, 364, 372, 378, 380, 396, 408, 414, 440, 444, 450, 456, 460, 468, 476, 480, 490, 492

Offset

1,1

Comments

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

a(n) = A178212(n) for n <= 52, possibly more. [Reinhard Zumkeller, May 24 2010]

Links

G. C. Greubel, Table of n, a(n) for n = 1..1200

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[6500], A123709[#] == 16 &] (* G. C. Greubel, Apr 22 2017 *)

Prog

(PARI)is(n)=my(M=matrix(n, n, r, c, r\c)^-1); sum(k=1, n, M[n, k]!=0)==16 \\ Charles R Greathouse IV, Feb 09 2012

Crossrefs

Cf. A123706, A123709, A123710, A123711, A010766.

Sequence in context: A261375 A349758 A217740 * A178212 A182855 A350371

Adjacent sequences: A123709 A123710 A123711 * A123713 A123714 A123715

Keyword

nonn

Author

Paul D. Hanna, Oct 09 2006

Status

approved