OFFSET
1,1
EXAMPLE
a(1) = 8 because the sum of the anti-divisors of 8 is 8 and of 9 is 8 again;
a(2) = 55 because the sum of the anti-divisors of 55 is 74 and of 57 is 74 again.
MAPLE
with(numtheory): P:=proc(q) local a, b, i, j, k, n; for i from 0 to q do for n from 1 to q do
k:=0; j:=n; while j mod 2 <> 1 do k:=k+1; j:=j/2; od;
a:=sigma(2*n+1)+sigma(2*n-1)+sigma(n/2^k)*2^(k+1)-6*n-2;
k:=0; j:=n+i; while j mod 2 <> 1 do k:=k+1; j:=j/2; od;
b:=sigma(2*(n+i)+1)+sigma(2*(n+i)-1)+sigma((n+i)/2^k)*2^(k+1)-6*(n+i)-2;
if a=b then print(n); break; fi; od; od; end: P(10^5);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paolo P. Lava, Jan 24 2018
STATUS
approved