OFFSET
2,1
COMMENTS
a(p+1) = p+2 if p is a prime.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 2..10000
EXAMPLE
a(8) = 9: the partitions are ( 1,7),(2,6),(3,5),(4,4) which give 9,15,10,14 as the sum of sigma functions of both the parts.
MATHEMATICA
Table[Min[Total[#]&/@(DivisorSigma[1, #]&/@({#, n-#}&/@Range[n/2]))], {n, 2, 80}] (* Harvey P. Dale, Oct 05 2017 *)
PROG
(PARI) a(n)=my(best=sigma(n-1)+1); for(k=2, n\2, best=min(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