A195144 - OEIS

%I #19 Mar 30 2012 18:53:49

%S 5,8,895799

%N Reversal of n equals the sum of the reversals of the anti-divisors of n.

%C Like A069942 but using anti-divisors. No other terms up to 3*10^10.

%e The first two terms are banal cases: anti-divisors of 5 are 2 and 3 and their reversals are again 5, 2 and 3 and 2+3 = 5. The same for 8: 3+5 = 8. Anti-divisors of 895799 are 2, 3, 199, 597, 3001, 9003, 597199 and 2+3+991+795+1003+3009+991795 = 997598.

%p Rev:=proc(n)

%p local a,i,k;

%p   i:=convert(n,base,10); a:=0;

%p   for k from 1 to nops(i) do a:=a*10+i[k]; od;

%p   a;

%p end:

%p P:=proc(j)

%p local h,m,n,r;

%p for m from 3 to j  do

%p   h:=0;

%p   for r from 2 to m-1 do

%p     if abs((m mod r)-r/2)<1 then h:=h+Rev(r); print(r); fi;

%p   od;

%p   if h=Rev(m) then print(m); fi;

%p od;

%p end:

%p P(1000000);

%Y Cf. A066272, A069942.

%K nonn,hard,base,bref,more

%O 1,1

%A _Paolo P. Lava_ and _Donovan Johnson_, Sep 12 2011