OFFSET
1,2
COMMENTS
In sequence A007429 are added all values of sigma(d) of all divisors d of numbers n, in sequence A206028 are added only distinct values of sigma(d) of all divisors d of numbers n and in sequence a(n) are added numbers k (1<=k<=sigma(n)) such that sigma(d) = k has no solution for neither divisor d of number n.
EXAMPLE
For n=6 -> divisors d of 6: 1,2,3,6; corresponding values of sigma(d): 1,3,4,12; a(6) = Sum of k = 2+5+6+7+8+9+10+11 = 58.
MATHEMATICA
Table[Total[Complement[Range[DivisorSigma[1, n]], DivisorSigma[1, Divisors[n]]]], {n, 100}] (* T. D. Noe, Feb 10 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Feb 03 2012
STATUS
approved