login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A087371 Smallest k such that 10^k + 2n-1 is a prime >10, or 0 if no such k exists. Index of the smallest power of 10 which when increased by the n-th odd number yields a prime. 1
1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 2, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 2, 1, 0, 1, 0, 0, 1, 2, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 3, 2, 0, 0, 1, 0, 1, 2, 0, 1, 1, 0, 2, 0, 0, 1, 1, 0, 0, 1, 0, 2, 1, 0, 1, 4, 0, 1, 0, 0, 1, 1, 0, 0, 2, 0, 1, 1, 0, 1, 1, 0, 2, 0, 0, 6, 1, 0, 0, 2, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,20

COMMENTS

Most of the terms are 0, 1 or 2. Subsidiary sequence: Index of the first occurrence of n. Conjecture: There exists a finite M such that a(n) < M for all n.

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

a(10) = 1 as 10^1 + 19 = 29 is a prime.

CROSSREFS

Sequence in context: A309475 A221314 A326642 * A307597 A307056 A112762

Adjacent sequences:  A087368 A087369 A087370 * A087372 A087373 A087374

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Sep 09 2003

EXTENSIONS

More terms from David Wasserman, May 24 2005

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 23 20:17 EDT 2019. Contains 328373 sequences. (Running on oeis4.)