Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A128510
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A128510 Multiply the sum of the extended factors of a composite by the integer itself to see whether the product is one away from a prime. +0
1
4, 6, 9, 10, 12, 14, 16, 20, 21, 25, 26, 28, 33, 34, 35, 36, 38, 40, 42, 44, 46, 50, 51, 52, 54, 55, 56, 60, 64, 65, 68 (list; graph; listen)
OFFSET

1,1

COMMENT

Fifty trials eventuated in 40 primes being one away or splitting a twin. It is curious that the products were all even except for 27, 3*3*3*27=243, and for 63, 3*3*7*63=819. One wonders if an extension would prove this to be the rule.

REFERENCES

Similar to A066073.

FORMULA

Find the sum of the extended factors of an integer, multiply it by the integer, and see if the product is one away from a prime or splits a twin prime.

EXAMPLE

Take 52=2*2*13, having the sum of its factors equaling 2+2+13=17.

Multiply 52 by 17 to get 884, which is one away from prime 883.

CROSSREFS

Sequence in context: A010447 A112082 A051278 this_sequence A120329 A123249 A010428

Adjacent sequences: A128507 A128508 A128509 this_sequence A128511 A128512 A128513

KEYWORD

nonn,uned

AUTHOR

J. M. Bergot (thekingfishb(AT)yahoo.ca), May 07 2007

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified September 5 19:27 EDT 2008. Contains 143485 sequences.


AT&T Labs Research