|
%I #9 May 19 2019 11:36:51
%S 0,2,3,2,5,8,7,10,3,12,11,18,13,16,18,10,17,26,19,27,24,24,23,38,5,28,
%T 30,37,29,47,31,42,36,36,40,33,37,40,42,57,41,64,43,57,57,48,47,78,7,
%U 62,54,67,53,80,60,79,60,60,59,104,61,64,75,42,70,96,67,87,72,93,71,122,73
%N Sum of even-indexed divisors of n.
%C a(p)=p iff p prime.
%e 10 has divisors 1,2,5 and 10. The even indices yield 2 and 10, so a(10)=12.
%t Prepend[Table[Total[Transpose[Partition[Divisors[n],2]][[2]]],{n,2,100}],0] (* _Harvey P. Dale_, Jan 17 2011 *)
%o (PARI) for (n=1,100,s=0; c=0; fordiv(i=n,i,c++; if (c%2==0,s+=i)); print1(","s))
%Y Cf. A086988.
%K nonn
%O 1,2
%A _Jon Perry_, Jul 27 2003
|
