A391720 a(n) is the smallest k for which A243917(k) = n.

3, 1, 2, 16, 10, 30, 42, 100, 110, 90, 216, 240, 210, 270, 462, 450, 864, 810, 720, 630, 1050, 1080, 1440, 1980, 1680, 1800, 2310, 1890, 2160, 3240, 4032, 3150, 7140, 3780, 4320, 5400, 6600, 9000, 6480, 5040, 6930, 9450, 7560, 9240, 10800, 10920, 13200, 13440

Offset

0,1

Links

Robert Israel, Table of n, a(n) for n = 0..500

Maple

g:= proc(n) local D; D:= NumberTheory:-Divisors(n);
  nops(D minus (D +~ 2) minus (D -~ 2))
end proc:
N:= 100: # for a(0)..a(N)
V:= Array(0..N): count:= 0:
for k from 1 while count < N+1 do
  v:= g(k);
  if v <= N and V[v] = 0 then count:= count+1; V[v]:= k; fi;
od:
convert(V, list); # Robert Israel, Mar 16 2026

Crossrefs

Cf. A005179, A243865, A243917, A391675.

Sequence in context: A126038 A088363 A300839 * A397656 A179175 A274635

Adjacent sequences: A391717 A391718 A391719 * A391721 A391722 A391723

Keyword

nonn

Author

Juri-Stepan Gerasimov, Feb 25 2026

Extensions

Corrected and extended by Sean A. Irvine, Mar 03 2026

Status

approved