OFFSET
1,1
EXAMPLE
49 = concat(4,9); phi(4) = 2, phi(9) = 6, sigma(49) = 57; 2 + 6 = 8 = 57 - 49.
169 = concat(16,9); phi(16) = 8, phi(9) = 6, sigma(169) = 183; 8 + 6 = 14 = 183-169.
MAPLE
with(numtheory); P:=proc(q) local a, b, i, n; for n from 1 to q do
for i from 1 to ilog10(n) do a:=trunc(n/10^i); b:=n-a*10^i;
if phi(a)+phi(b)=sigma(n)-n then print(n); break;
fi; od; od; end: P(10^9);
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Paolo P. Lava, Feb 03 2015
STATUS
approved