OFFSET
0,2
EXAMPLE
a(4) = 8 because eight is the fourth nonprime number and GCD(4,8) > GCD(3,6).
MATHEMATICA
r=0; Do[a = GCD[n, n - PrimePi[n] ]; If[a > r, r = a; Print[n]], {n, 1, 10^5} ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Nov 13 2000
STATUS
approved