A349475
a(n) is the least number k such that A349474(k) = n, or -1 if no such k exists.
Original entry on oeis.org
1, 2, 5, 4, 21, 25, 16, 36, 106, 712, 1588, 3775, 900, 4356, 18496, 14400, 45700, 87003, 135445, 229543, 554216, 937019, 1764724, 3431952, 3431088, 10217808, 21357233, 36972202, 42436276, 79056144, 235027304, 261540000, 530582544, 705929608, 1371526825, 1127941321
Offset: 1
a(3) = 5 since 5 is the least number k such that A349474(k) = 3.
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cflen[n_] := Length @ 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 = cflen[n]; If[i <= len && s[[i]] == 0, c++; s[[i]] = n]; n++]; TakeWhile[s, # > 0 &]]; seq[20, 10^7]
A349498
a(n) is the least number k such that A349497(k) = n, or -1 if no such k exists.
Original entry on oeis.org
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
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
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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]