login
A088740
Greatest semiprime divisor of n-th composite number.
2
4, 6, 4, 9, 10, 6, 14, 15, 4, 9, 10, 21, 22, 6, 25, 26, 9, 14, 15, 4, 33, 34, 35, 9, 38, 39, 10, 21, 22, 15, 46, 6, 49, 25, 51, 26, 9, 55, 14, 57, 58, 15, 62, 21, 4, 65, 33, 34, 69, 35, 9, 74, 25, 38, 77, 39, 10, 9, 82, 21, 85, 86, 87, 22, 15, 91, 46, 93, 94, 95, 6, 49, 33, 25
OFFSET
1,1
MATHEMATICA
Reap[Do[If[! PrimeQ[n], fl = Flatten[Table[#[[1]], {#[[2]]}] & /@ FactorInteger[n]]; Sow[fl[[-1]]*fl[[-2]]]], {n, 4, 1200}]][[2, 1]]; (* Zak Seidov, Mar 18 2013 *)
gsd[n_]:=Max[Select[Divisors[n], PrimeOmega[#]==2&]]; gsd/@Select[Range[ 200], CompositeQ] (* Harvey P. Dale, May 08 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 12 2003
STATUS
approved