OFFSET
1,2
COMMENTS
Often, but not always, a(n)=n+A054024(n). The exceptions to this rule are at n=24, 36, 48, 60, 72, 84,90, 96, 108, ... - R. J. Mathar, Mar 14 2007
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
12's divisors are 1,2,3,4,6 and 12. Adding the divisors in order we have:
1 = 1, 1+2 = 3, 1+2+3 = 6, 1+2+3+4 = 10, 1+2+3+4+6 = 16 and 1+2+3+4+6+12 = 28.
Of these sums, 1+2+3+4+6 = 16 is the lowest which is >= 12. So a(12) = 16.
MAPLE
A117553 := proc(n) local divs, a, i ; divs := numtheory[divisors](n) ; a := op(1, divs) ; i := 1 ; while a < n do i := i+1 ; a := a+op(i, divs) ; od ; RETURN(a) ; end: for n from 1 to 80 do printf("%d, ", A117553(n)) ; od ; # R. J. Mathar, Mar 14 2007
MATHEMATICA
Table[Select[Accumulate[Divisors[n]], #>=n&, 1], {n, 80}]//Flatten (* Harvey P. Dale, Apr 05 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 28 2006
EXTENSIONS
More terms from R. J. Mathar, Mar 14 2007
STATUS
approved