|
Search: id:A061645
|
|
|
| A061645 |
|
a(n) = number of divisors of n-th perfect number. |
|
+0
13
|
|
| 4, 6, 10, 14, 26, 34, 38, 62, 122, 178, 214, 254, 1042, 1214, 2558, 4406, 4562, 6434, 8506, 8846, 19378, 19882, 22426, 39874, 43402, 46418, 88994, 172486, 221006, 264098, 432182, 1513678, 1718866, 2515574, 2796538, 5952442, 6042754
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
The number of divisors of n-th perfect number that are powers of 2 is equal to a(n)/2, assuming there are no odd perfect numbers. The number of divisors of n-th perfect number that are multiples of n-th Mersenne prime A000668(n) is also equal to a(n)/2, assuming there are no odd perfect numbers. (See A000043). - Omar E. Pol (info(AT)polprimos.com), Feb 28 2008
|
|
LINKS
|
O. E. Pol, Determinacion geometrica de los numeros primos y perfectos.
|
|
FORMULA
|
a(n) = A000005[A000396(n)] = 2*A000043(n)
a(n) = floor{log_2(A000396(n))} + 2. - Lekraj Beedassy (blekraj(AT)yahoo.com), Aug 21 2004
|
|
EXAMPLE
|
8128 = 2*2*2*2*2*2*127 with 14 divisors.
|
|
CROSSREFS
|
Cf. A000005, A000396, A000043.
Cf. A000668.
Sequence in context: A049632 A061227 A000066 this_sequence A084372 A140611 A076957
Adjacent sequences: A061642 A061643 A061644 this_sequence A061646 A061647 A061648
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu), Jun 14 2001
|
|
|
Search completed in 0.002 seconds
|
