cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A037159 Consider the trajectory of n under the iteration of a map which sends x to 3x - sigma(x) if this is >= 0; otherwise the iteration stops. The sequence gives values of n which eventually reach 0.

Original entry on oeis.org

82, 120, 280, 672, 1464, 3048, 4964, 5568, 5688, 7666, 8969, 9176, 9288, 9514, 9616, 9706, 10132, 10186, 10232, 10478, 11496, 11884, 11914, 12232, 12320, 12820, 13248, 13842, 13854, 13866, 14848, 15076, 15098, 15196, 15364, 15586, 15892
Offset: 1

Views

Author

Naohiro Nomoto

Keywords

Comments

A perfect number is a fixed point of this map.

Examples

			82 -> 120 -> 0.

Crossrefs

To see why 1, 16 and 23 are not in the sequence, see A058541, A058542 and A058545.
Cf. A033885, A033945, A033946, A037160.

Programs

Extensions

Better description from Jud McCranie, Dec 24 2000
Definition clarified by Harvey P. Dale, Jul 30 2020

A058541 Trajectory of 1 under map that sends x to 3x - sigma(x).

Original entry on oeis.org

1, 2, 3, 5, 9, 14, 18, 15, 21, 31, 61, 121, 230, 258, 246, 234, 156, 76, 88, 84, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28
Offset: 0

Views

Author

N. J. A. Sloane, Jud McCranie, Dec 24 2000

Keywords

Crossrefs

Cf. A037159, A058542, A058545.

Programs

  • Mathematica
    NestList[3#-DivisorSigma[1,#]&,1,70] (* Harvey P. Dale, Jul 23 2012 *)

A058545 Trajectory of 23 under map that sends x to 3x - sigma(x), where sigma(x) is the sum of the divisors of x.

Original entry on oeis.org

23, 45, 57, 91, 161, 291, 481, 911, 1821, 3031, 5621, 9759, 16261, 29199, 48661, 97321, 180731, 361461, 595359, 914661, 1302543, 1810989, 2732295, 3594645, 4393215, 5513805, 5482215, 6700245, 8913663, 12588669, 19116087, 31171125
Offset: 0

Views

Author

N. J. A. Sloane, Dec 24 2000

Keywords

Crossrefs

Cf. A037159, A058541, A058542.
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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