a(n) is multiplicative with a(2) = 1; a(4) = 2; a(2^i) = 2^(i-2)+2 if i>2; a(p^i) = 1+(p-1)*p^(i-1)/2 if prime p>2 and i>0.
A007897
a(n) is multiplicative with a(2) = 1; a(4) = 2; a(2^i) = 2^(i-2)+2 if i>2; a(p^i) = 1+(p-1)*p^(i-1)/2 if prime p>2 and i>0.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =2a(4) =3a(5) =2a(6) =4a(7) =4a(8) =4a(9) =3a(10) =6a(11) =4a(12) =7a(13) =4a(14) =6a(15) =6a(16) =9a(17) =4a(18) =10a(19) =6a(20) =8a(21) =6a(22) =12a(23) =8a(24) =11a(25) =7a(26) =10a(27) =8a(28) =15a(29) =6
External references
- oeis: A007897