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A349498
a(n) is the least number k such that A349497(k) = n, or -1 if no such k exists.
0
1, 6, 24, 170, 140, 270, 1140, 630, 1400, 4420, 2016, 8680, 11704, 18620, 8190, 20196, 12960, 90860, 13860, 30800, 55860, 148770, 51408, 30240, 78120, 242060, 153120, 282555, 65520, 564564, 268128, 381150, 798560, 592515, 535680, 1503216, 318240, 664020, 726180, 790020
OFFSET
1,2
EXAMPLE
The elements of the continued fractions of the harmonic mean of the divisors of the first 10 terms are:
n a(n) elements
-- ---- --------
1 1 1
2 6 2
3 24 3,5
4 170 4,5,16
5 140 5
6 270 6
7 1140 8,7
8 630 8,13
9 1400 9,31
10 4420 10,44,10
MATHEMATICA
f[n_] := Min[ContinuedFraction[DivisorSigma[0, n] / DivisorSigma[-1, n]]]; seq[len_, nmax_] := Module[{s = Table[0, {len}], c = 0, n = 1, i}, While[c < len && n < nmax, i = f[n]; If[i <= len && s[[i]] == 0, c++; s[[i]] = n]; n++]; s]; seq[25, 10^6]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 20 2021
STATUS
approved