|
%I #17 Mar 01 2019 15:29:54
%S 0,1,1,5,1,14,1,21,10,30,1,66,1,54,35,85,1,131,1,146,59,126,1,274,26,
%T 174,91,266,1,400,1,341,131,294,75,615,1,366,179,610,1,736,1,626,341,
%U 534,1,1106,50,755,299,866,1,1184,147,1114,371,846,1,1860,1,966,581,1365
%N Sum of squares of proper divisors of n.
%C a(n) = A001157(n) - n^2.
%C a(n) = 1 if and only if n is prime.
%H T. D. Noe, <a href="/A067558/b067558.txt">Table of n, a(n) for n=1..10000</a>
%F Dirichlet g.f.: zeta(s-2)*(zeta(s) - 1). - _Ilya Gutkovskiy_, Sep 08 2016
%e a(12) = 1^2 + 2^2 + 3^2 + 4^2 + 6^2 = 1 + 4 + 9 + 16 + 36 = 66.
%t Table[DivisorSigma[2, n] - n^2, {n, 1, 64}] (* _Jean-François Alcover_, Mar 01 2019 *)
%o (PARI) a(n)=sigma(n,2)-n^2 \\ _Charles R Greathouse IV_, Dec 07 2011
%Y Cf. A001157, A032741.
%K nonn
%O 1,4
%A _Reinhard Zumkeller_, Jan 29 2002
|
