OFFSET
1,1
COMMENTS
For n-bit arithmetic, m=a(n) - 1 is the largest number for which sigma_2(m) can be computed without overflow. For 31, 32, 63 and 64 bits, the numbers are respectively 36959, 52559, 2389186799 and 3380176799.
LINKS
T. D. Noe, Table of n, a(n) for n=1..64
FORMULA
For large n, a(n) ~ sqrt(2)*a(n-1).
MATHEMATICA
k=1; Table[While[DivisorSigma[2, k]<2^n, k++ ]; k, {n, 40}]
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Jul 11 2008
STATUS
approved