OFFSET
1,2
COMMENTS
If n is prime, a(n) = n^2. - Robert Israel, Nov 07 2019
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
For n = 4, the largest prime dividing 1*4=4 is 2. The largest prime dividing 2*4=8 is 2. The largest prime dividing 3*4=12 is 3. And the largest prime dividing 4*4=16 is 2. So a(4) = 2+2+3+2 = 9.
MAPLE
lpf:= proc(n) option remember; max(numtheory:-factorset(n)) end proc:
f:= proc(n) local k; add(max(lpf(k), lpf(n)), k=1..n) end proc;
f(1):= 0:
map(f, [$1..100]); # Robert Israel, Nov 07 2019
MATHEMATICA
lpf[n_] := lpf[n] = Max[FactorInteger[n][[All, 1]]];
a[n_] := Sum[Max[lpf[k], lpf[n]], {k, 1, n}];
a[1] = 0;
Array[a, 100] (* Jean-François Alcover, Jul 23 2020, after Maple *)
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Leroy Quet, Jul 05 2008
EXTENSIONS
Extended by Ray Chandler, Jun 22 2009
STATUS
approved