This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A325121 #5 Mar 30 2019 08:36:50
%S A325121 0,1,1,2,2,2,1,3,2,3,2,3,2,2,3,4,3,3,1,4,2,3,2,4,4,3,3,3,2,4,3,5,3,4,
%T A325121 3,4,2,2,3,5,3,3,3,4,4,3,4,5,2,5,4,4,1,4,4,4,2,3,2,5,2,4,3,6,4,4,3,5,
%U A325121 3,4,2,5,3,3,5,3,3,4,3,6,4,4,4,4,5,4,3
%N A325121 Sum of binary digits of the prime indices of n.
%C A325121 The sum of binary digits of an integer is the number of 1's in its binary representation. A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
%F A325121 Totally additive with a(prime(n)) = A000120(n).
%t A325121 Table[Sum[pr[[2]]*DigitCount[PrimePi[pr[[1]]],2,1],{pr,FactorInteger[n]}],{n,100}]
%Y A325121 Cf. A000120, A000720, A001222, A019565, A048881, A070939, A112798.
%Y A325121 Cf. A325103, A325104, A325106, A325118, A325119.
%Y A325121 Other totally additive sequences: A056239, A302242, A318994, A318995, A325033, A325034, A325120, A325122.
%K A325121 nonn
%O A325121 1,4
%A A325121 _Gus Wiseman_, Mar 29 2019