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 A080773 #22 Jul 30 2025 01:00:27
%S A080773 0,1,2,2,2,3,3,3,4,3,3,4,3,4,4,4,2,5,3,4,5,4,4,5,4,4,6,5,4,5,5,5,5,3,
%T A080773 5,6,3,4,5,5,3,6,4,5,6,5,5,6,6,5,4,5,4,7,5,6,5,5,5,6,5,6,7,6,5,6,3,4,
%U A080773 6,6,4,7,3,4,6,5,6,6,5,6,8,4,4,7,4,5,6,6,4,7,6,6,7,6,5,7,3,7,7,6,4,5,5,6,7
%N A080773 In binary representation: sum of number of 1's in prime factors of n (with repetition).
%H A080773 Amiram Eldar, <a href="/A080773/b080773.txt">Table of n, a(n) for n = 1..10000</a>
%F A080773 Totally additive with a(p) = A000120(p). - _Amiram Eldar_, Jul 30 2025
%e A080773 a(20) = a(2*2*5) = a('10' * '10' * '101') = 1+1+2 = 4.
%t A080773 sn1[n_]:=Total[Flatten[IntegerDigits[#,2]&/@Flatten[Table[#[[1]],{#[[2]]}] &/@ FactorInteger[n]]]]; Join[{0},Rest[Array[sn1,110]]] (* _Harvey P. Dale_, Nov 19 2013 *)
%o A080773 (PARI) a(n) = my(f=factor(n)); sum(k=1, #f~, hammingweight(f[k,1])*f[k,2]); \\ _Michel Marcus_, Aug 28 2019
%Y A080773 Cf. A000120, A007088, A134599 (base 3).
%K A080773 nonn,base,easy
%O A080773 1,3
%A A080773 _Reinhard Zumkeller_, Mar 10 2003