|
Search: id:A141847
|
|
|
| A141847 |
|
Least number k such that sigma2(k) >= 2^n. |
|
+0
1
|
|
| 2, 2, 3, 4, 6, 8, 10, 15, 20, 28, 40, 54, 78, 108, 156, 216, 300, 420, 600, 840, 1188, 1680, 2340, 3360, 4680, 6600, 9240, 13200, 18480, 26400, 36960, 52560, 73920, 105000, 147840, 209160, 294840, 415800, 589680, 831600, 1178100, 1663200, 2353680
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
For n-bit arithmetic, m=a(n)-1 is the largest number for which sigma2(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
|
Cf. A001157 (sigma2).
Sequence in context: A066447 A035542 A130081 this_sequence A089333 A098492 A103632
Adjacent sequences: A141844 A141845 A141846 this_sequence A141848 A141849 A141850
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
T. D. Noe (noe(AT)sspectra.com), Jul 11 2008
|
|
|
Search completed in 0.002 seconds
|
