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A123712 Indices n such that 16 = A123709(n) = number of nonzero terms in row n of triangle A123706. 5
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 (list; graph; refs; listen; history; text; internal format)
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 A217740 * A178212 A182855 A009129 A174292

Adjacent sequences:  A123709 A123710 A123711 * A123713 A123714 A123715

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Oct 09 2006

STATUS

approved

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Last modified July 21 04:27 EDT 2017. Contains 289632 sequences.