A126602 a(1)=2^3*5*7*29=8120; for n>1, a(n) = (-1)sigma(a(n-1)).

8120, 8736, 8784, 19140, 11200, 21750, 8624, 15950, 8120, 8736, 8784, 19140, 11200, 21750, 8624, 15950, 8120, 8736, 8784, 19140, 11200, 21750, 8624, 15950, 8120, 8736, 8784, 19140, 11200, 21750, 8624, 15950, 8120, 8736, 8784, 19140

Offset

1,1

Comments

(-1)sigma is defined in A049060. This is a cyclic sequence whose period is 8, so these numbers are called "(-1)sigma sociable numbers of order 8".

Links

Table of n, a(n) for n=1..36.

Example

The numbers are 2^3*5*7*29, 2^5*3*7*13, 2^4*3^2*61, 2^2*3*5*11*29, 2^6*5^2*7, 2*3*5^3*29, 2^4*7^2*11, 2*5^2*11*29, then repeat.

Mathematica

LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 1}, {8120, 8736, 8784, 19140, 11200, 21750, 8624, 15950}, 50] (* or *) PadRight[{}, 50, {8120, 8736, 8784, 19140, 11200, 21750, 8624, 15950}] (* Harvey P. Dale, Jan 23 2025 *)

Crossrefs

Sequence in context: A163045 A069368 A068758 * A209845 A025288 A025306

Adjacent sequences: A126599 A126600 A126601 * A126603 A126604 A126605

Keyword

nonn

Author

N. J. A. Sloane, Feb 14 2008, based on a posting to the Sequence Fans Mailing List by Yasutoshi Kohmoto, Feb 02 2005

Status

approved