OFFSET
2,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 2..10000
EXAMPLE
a(8) = 6, the partitions are ( 1,7),(2,6),(3,5),(4,4) which give 9, 15,10,14 as the sum of the sigma function of both the parts.
MATHEMATICA
a[n_] := Max[Total[DivisorSigma[1, #]]& /@ IntegerPartitions[n, {2}]]; Table[a[n], {n, 2, 100}] (* Jean-François Alcover, Dec 26 2013 *)
PROG
(PARI) a(n)=my(best=sigma(n-1)+1); for(k=2, n\2, best=max(best, sigma(k)+sigma(n-k))); best \\ Charles R Greathouse IV, Apr 06 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Jul 08 2003
EXTENSIONS
More terms from David Wasserman, Feb 10 2005
STATUS
approved