login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A095188 Smallest prime formed by the digit string after decimal point of n^(1/2), or 0 if no such prime exists. 1
0, 41, 7, 0, 2, 449, 645751, 82842712474619, 0, 162277, 3, 464101615137754587054892683011, 605551, 7, 87298334620741688517926539978239961, 0, 1231, 2, 3, 47, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Conjecture: a(n) is nonzero if n is not a perfect square.

For n=22, no provable primes were found with fewer than 256 digits. - Wouter Meeussen, Jun 04 2004

LINKS

Table of n, a(n) for n=1..21.

EXAMPLE

a(7) = 645751 as 7^(1/2) = 2.64575131106459059... and the least prime is 645751.

MATHEMATICA

<< NumberTheory`PrimeQ`; it = Table[{n, k = 1; While[temp = Floor[10^k FractionalPart[n^(1/2)]]; k < 256 && (temp === 1 || ! ProvablePrimeQ[temp]), k++ ]; temp, k}, {n, 2, 21}]

CROSSREFS

Sequence in context: A198190 A106424 A126636 * A215540 A107813 A198162

Adjacent sequences:  A095185 A095186 A095187 * A095189 A095190 A095191

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Jun 02 2004

EXTENSIONS

Corrected and extended by Wouter Meeussen, Jun 04 2004

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 July 11 20:03 EDT 2020. Contains 335652 sequences. (Running on oeis4.)