OFFSET
1,1
EXAMPLE
If n = 132011, starting from the most significant digit, let us cut the number into the set 1, 13, 132, 1320, 13201. We have:
phi(1) = 1;
phi(13) = 12;
phi(132) = 40;
phi(1320) = 320;
phi(13201) = 12852
and 1 + 12 + 40 + 320 + 12852 = 13225 = sigma(132011) - 132011.
MAPLE
with(numtheory); P:=proc(q) local a, k, n;
for n from 2 to q do a:=0; k:=1; while trunc(n/10^k)>0 do a:=a+phi(trunc(n/10^k)); k:=k+1; od;
if sigma(n)-n=a then print(n); fi; od; end: P(10^9);
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Paolo P. Lava, Apr 14 2014
EXTENSIONS
a(15)-a(29) from Giovanni Resta, Apr 15 2014
STATUS
approved