OFFSET
1,4
FORMULA
G.f.: Sum_{n>=1} A000010(n)*x^(n^2)/(1-x^n). - Mircea Merca, Feb 23 2014
EXAMPLE
a(30) = phi(1) + phi(2) + phi(3) + phi(5) = 1 + 1 + 2 + 4 = 8 because 1, 2, 3 and 5 are the positive divisors of 30 which are <= sqrt(30).
MAPLE
A070966 := proc(n)
local a, k ;
a := 0 ;
for k in numtheory[divisors](n) do
if k^2 <= n then
a := a+numtheory[phi](k) ;
end if;
end do:
a ;
end proc: # R. J. Mathar, May 27 2016
PROG
(PARI) a(n) = sumdiv(n, d, eulerphi(d)*(d^2 <= n)); \\ Michel Marcus, Dec 19 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, May 16 2002
STATUS
approved