

A123711


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


5



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
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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: A036456 A102467 A126706 * A200511 A059404 A242416
Adjacent sequences: A123708 A123709 A123710 * A123712 A123713 A123714


KEYWORD

nonn


AUTHOR

Paul D. Hanna, Oct 09 2006


STATUS

approved



