This site is supported by donations to The OEIS Foundation.

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A139247 Triangle read by rows: row n lists the divisors of n-th perfect number A000396(n) that are multiples of n-th Mersenne prime A000668(n). 3
 3, 6, 7, 14, 28, 31, 62, 124, 248, 496, 127, 254, 508, 1016, 2032, 4064, 8128, 8191, 16382, 32764, 65528, 131056, 262112, 524224, 1048448, 2096896, 4193792, 8387584, 16775168, 33550336, 131071, 262142, 524284, 1048568, 2097136, 4193792 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also, row n list the divisors of n-th perfect number that are not powers of 2. First term of row n is the n-th Mersenne prime A000668(n). Last term of row n is the n-th perfect number A000396(n). Row n has A000043(n) terms. The sum of row n is equal to A133049(n), the square of n-th Mersenne prime A000668(n). LINKS EXAMPLE Triangle begins: 3, 6, 7, 14, 28 31, 62, 124, 248, 496 127, 254, 508, 1016, 2032, 4064, 8128 ========================================================== Row .... First term ..... Last term ....... Row sum ...... n ..... (A000668(n)) ... (A000396(n)) ... (A000668(n)^2) . ========================================================== 1 ............ 3 .............. 6 ......... 3^2 = 9 2 ............ 7 ............. 28 ......... 7^2 = 49 3 ........... 31 ............ 496 ........ 31^2 = 961 4 .......... 127 ........... 8128 ....... 127^2 = 16129 5 ......... 8191 ....... 33550336 ...... 8191^2 = 67092481 CROSSREFS Cf. A000043, A000396, A000668, A018254, A018487, A133024, A133025, A133031, A133049, A135652, A135653, A135654, A135655. Sequence in context: A056055 A070523 A233757 * A124611 A281900 A266615 Adjacent sequences:  A139244 A139245 A139246 * A139248 A139249 A139250 KEYWORD nonn,tabf AUTHOR Omar E. Pol, Apr 22 2008 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 17 10:30 EST 2019. Contains 319218 sequences. (Running on oeis4.)