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%I #22 Dec 19 2017 03:06:16
%S 1,1,1,2,1,2,1,2,3,2,1,4,1,2,3,4,1,4,1,4,3,2,1,6,5,2,3,4,1,8,1,4,3,2,
%T 5,8,1,2,3,8,1,6,1,4,7,2,1,8,7,6,3,4,1,6,5,10,3,2,1,12,1,2,9,8,5,6,1,
%U 4,3,12,1,12,1,2,7,4,7,6,1,12,9,2,1,14,5,2,3,8,1,16,7,4,3,2,5,12,1,8,9,12
%N a(n) = Sum_{k|n, k<=sqrt(n)} phi(k); where the sum is over the positive divisors, k, of n, which are <= the square root of n; and phi(k) is the Euler totient function.
%F G.f.: Sum_{n>=1} A000010(n)*x^(n^2)/(1-x^n). - _Mircea Merca_, Feb 23 2014
%e 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).
%p A070966 := proc(n)
%p local a,k ;
%p a := 0 ;
%p for k in numtheory[divisors](n) do
%p if k^2 <= n then
%p a := a+numtheory[phi](k) ;
%p end if;
%p end do:
%p a ;
%p end proc: # _R. J. Mathar_, May 27 2016
%o (PARI) a(n) = sumdiv(n, d, eulerphi(d)*(d^2 <= n)); \\ _Michel Marcus_, Dec 19 2017
%Y Cf. A000010, A066839.
%K nonn
%O 1,4
%A _Leroy Quet_, May 16 2002
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