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%I #9 Dec 13 2015 01:00:31
%S 0,2,3,0,5,1,7,2,0,3,11,3,13,5,2,0,17,2,19,5,4,9,23,1,0,11,3,7,29,4,
%T 31,2,8,15,2,0,37,17,10,3,41,6,43,11,5,21,47,3,0,2,14,13,53,1,6,5,16,
%U 27,59,2,61,29,7,0,8,10,67,17,20,4,71,2,73,35
%N Alternating sum of all prime factors of n; primes nonincreasing, starting with the largest prime factor: A006530(n).
%C a(n) = 0 iff n square, a(A000290(n)) = 0;
%C a(n) = n iff n prime, a(A000040(n)) = A000040(n).
%H Harvey P. Dale, <a href="/A071322/b071322.txt">Table of n, a(n) for n = 1..1000</a>
%e 72 = 2*2*2*3*3, therefore a(72) = 3 - 3 + 2 - 2 + 2 = 2;
%e 90 = 2*3*3*5, therefore a(90) = 5 - 3 + 3 - 2 = 3.
%t aspf[n_]:=Total[Times@@@Partition[Riffle[Reverse[Flatten[Table[#[[1]],{#[[2]]}]&/@FactorInteger[n]]],{1,-1},{2,-1,2}],2]]; Join[{0}, Array[ aspf,80,2]] (* _Harvey P. Dale_, Apr 19 2015 *)
%Y Cf. A001414, A071324, a(n) = abs(A071321(n)).
%K nonn
%O 1,2
%A _Reinhard Zumkeller_, May 18 2002
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