cp's OEIS Frontend

A340969 a(n) is the first number k with A340967(k) = n.

%I A340969 #20 Feb 02 2021 16:14:12
%S A340969 1,2,8,12,14,54,158,159,203,2159,5999,8339,143098,85679,724919,
%T A340969 2417594,7415099,44026799,183578399,446036579
%N A340969 a(n) is the first number k with A340967(k) = n.
%F A340969 A340967(a(n)) = n.
%e A340969 a(3) = 12 because A340967(12) = 3 is the first occurrence of the value 3 in A340967.
%p A340969 sopfr:= proc(n) local t;
%p A340969   add(t[1]*t[2], t = ifactors(n)[2])
%p A340969 end proc:
%p A340969 f:= proc(n) local x, k;
%p A340969   x:= n;
%p A340969   for k from 1 do x:= n mod sopfr(x); if x <= 1 then return k fi od;
%p A340969 end proc:
%p A340969 f(1):= 0:
%p A340969 V:= Array(0..15): count:= 0:
%p A340969 for i from 1 while count < 16 do
%p A340969   v:= f(i);
%p A340969   if v <= 15 and V[v] = 0 then V[v]:= i; count:=count+1; fi
%p A340969 od:
%p A340969 convert(V,list);
%o A340969 (PARI)
%o A340969 f(n) = my(x=n,c=0,t); while(x > 1, c++; x = n % ((t=factor(x))[, 1]~*t[, 2])); c; \\ A340967
%o A340969 a(n) = for(k=1, oo, if(f(k) == n, return(k))); \\ _Daniel Suteu_, Feb 01 2021
%Y A340969 Cf. A340967.
%K A340969 nonn,more
%O A340969 0,2
%A A340969 _J. M. Bergot_ and _Robert Israel_, Jan 31 2021
%E A340969 a(17)-a(19) from _Daniel Suteu_, Feb 01 2021