|
Search: id:A070528
|
|
|
| A070528 |
|
Number of divisors of 10^n-1 (999...999 with n digits). |
|
+0
4
|
|
| 3, 6, 8, 12, 12, 64, 12, 48, 20, 48, 12, 256, 24, 48, 128, 192, 12, 640, 6, 384, 256, 288, 6, 2048, 96, 192, 96, 768, 96, 16384, 24, 6144, 128, 192, 384, 5120, 24, 24, 128, 6144, 48, 49152, 48, 4608, 1280, 192, 12, 16384, 48, 3072, 512, 1536, 48, 12288, 768
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
FORMULA
|
a(n) =A000005(A002283(n)) =sum_{d|n}A059892(d) =A070529(n)*(A007949(n)+3)/(A007949(n)+1)
|
|
EXAMPLE
|
a(7)=12 since the divisors of 9999999 are 1, 3, 9, 239, 717, 2151, 4649, 13947, 41841, 1111111, 3333333, 9999999.
|
|
CROSSREFS
|
Cf. A018282, A018766, A027894, A027893, A027892, A027891, A027890, A027889, A027895.
Sequence in context: A036434 A140400 A077148 this_sequence A122116 A126862 A092998
Adjacent sequences: A070525 A070526 A070527 this_sequence A070529 A070530 A070531
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
Henry Bottomley (se16(AT)btinternet.com), May 02 2002
|
|
|
Search completed in 0.002 seconds
|
