cp's OEIS Frontend

A067846 Least m such that A067513(m) = n.

%I A067846 #22 Jun 01 2022 01:58:06
%S A067846 1,2,4,16,12,48,36,60,120,252,180,480,360,540,720,1080,1620,1260,1680,
%T A067846 2160,3600,2520,3780,6720,6480,9240,5040,7560,15840,16380,10080,22680,
%U A067846 18480,32400,20160,15120,37800,32760,25200,40320,30240,73920,45360
%N A067846 Least m such that A067513(m) = n.
%C A067846 There are 57 terms less than 200000. - _David Wasserman_, Dec 20 2002
%H A067846 Robert G. Wilson v, <a href="/A067846/b067846.txt">Table of n, a(n) for n = 1..1276</a> (first 161 terms from Robert Israel)
%p A067846 N:= 80: # to get a(1)..a(N)
%p A067846 A067513:= n -> nops(select(t -> isprime(t+1), numtheory:-divisors(n))):
%p A067846 A:= Vector(N):
%p A067846 count:= 1: A[1]:= 1:
%p A067846 for n from 2 by 2 while count < N do
%p A067846   v:= A067513(n);
%p A067846   if v <= N and A[v]=0 then A[v]:= n; count:= count+1; fi
%p A067846 od:
%p A067846 convert(A, list); # _Robert Israel_, Jun 08 2018
%o A067846 (PARI) a067513(n) = sumdiv(n, d, isprime(d+1));
%o A067846 a(n) = {my(k=1); while(a067513(k) != n, k++); k;} \\ _Michel Marcus_, Jun 09 2018
%Y A067846 Cf. A067513, A183063.
%K A067846 nonn
%O A067846 1,2
%A A067846 _Vladeta Jovovic_, Feb 14 2002
%E A067846 More terms from _David Wasserman_, Dec 20 2002