OFFSET
1,6
FORMULA
a(n) = Sum_{i=1..floor(n/2)} [omega(i) = omega(n-i)], where [] is the Iverson bracket and omega is the number of distinct prime factors of n (A001221).
MATHEMATICA
Table[Sum[KroneckerDelta[PrimeNu[i], PrimeNu[n - i]], {i, Floor[n/2]}], {n, 100}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Apr 02 2020
STATUS
approved