A391720 - OEIS

%I #36 Mar 17 2026 05:38:56

%S 3,1,2,16,10,30,42,100,110,90,216,240,210,270,462,450,864,810,720,630,

%T 1050,1080,1440,1980,1680,1800,2310,1890,2160,3240,4032,3150,7140,

%U 3780,4320,5400,6600,9000,6480,5040,6930,9450,7560,9240,10800,10920,13200,13440

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

%H Robert Israel, <a href="/A391720/b391720.txt">Table of n, a(n) for n = 0..500</a>

%p g:= proc(n) local D; D:= NumberTheory:-Divisors(n);

%p   nops(D minus (D +~ 2) minus (D -~ 2))

%p end proc:

%p N:= 100: # for a(0)..a(N)

%p V:= Array(0..N): count:= 0:

%p for k from 1 while count < N+1 do

%p   v:= g(k);

%p   if v <= N and V[v] = 0 then count:= count+1; V[v]:= k; fi;

%p od:

%p convert(V,list); # _Robert Israel_, Mar 16 2026

%Y Cf. A005179, A243865, A243917, A391675.

%K nonn

%O 0,1

%A _Juri-Stepan Gerasimov_, Feb 25 2026

%E Corrected and extended by _Sean A. Irvine_, Mar 03 2026