OFFSET
1,3
LINKS
FORMULA
EXAMPLE
a(315) = a(3^2 * 5 * 7) = a(prime(2)^2 * prime(3) * prime(4)) = 2 * 4 = 8.
MATHEMATICA
a[1] = 1; a[n_] := PrimePi[FactorInteger[n] [[1, 1]]] PrimePi[ FactorInteger[ n] [[-1, 1]]]; Table[a[n], {n, 1, 80}]
PROG
(PARI) a(n) = if (n==1, 1, my(f=factor(n)[, 1]); primepi(vecmin(f))*primepi(vecmax(f))); \\ Michel Marcus, Mar 16 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 15 2020
STATUS
approved