Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A130827
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A130827 Least k >= 1 such that k^n+n is semiprime, or 0 if no such k exists. +0
2
3, 2, 1, 3, 1, 7, 3, 1, 1, 11, 2, 7, 1, 1, 7, 3, 5, 23, 4, 1, 1, 3, 2, 1, 1, 21, 14, 11, 12, 7, 16, 1, 1, 1, 26, 37, 1, 1, 4, 21, 6, 31, 4 (list; graph; listen)
OFFSET

1,1

COMMENT

k^n+n can be prime for not all n's (cf. A072883). What about semiprime k^n+n? For which n's a(n)=0? Cf. A097792 (n such that x^n+n is reducible), A072883 (Least k >= 1 such that k^n+n is prime, or 0 if no such k exists).

EXAMPLE

a(1)=3, a(2)=2, and a(3)=1 because

3^1+1=2^2+2=1^3+3=4=2*2 (semiprime),

a(4)=3 because 3^4+4=35=5*7 (semiprime), a(5)=1

because 1^5+1=6=2*3 (semiprime), a(6)=7 because

7^6+6=117655=5*23531 (semiprime).

CROSSREFS

Cf. A072883, A097792.

Sequence in context: A079587 A112745 A036585 this_sequence A070309 A130784 A119910

Adjacent sequences: A130824 A130825 A130826 this_sequence A130828 A130829 A130830

KEYWORD

more,nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), Aug 18 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 July 23 17:35 EDT 2008. Contains 142285 sequences.


AT&T Labs Research