OFFSET
1,4
FORMULA
a(n) = b(0, n), b(m, n) = 1 + sum(b(i, j): m<i<j<n & i+j=sigma(n)).
PROG
(PARI) a(n)=my(v=partitions(sigma(n), n)); sum(i=1, #v, #vecsort(v[i], , 8)==#v[i]) \\ Charles R Greathouse IV, Feb 14 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Dec 27 2002
STATUS
approved