login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A089328 Smallest prime of the form the concatenation r*k for r = 1 to n followed by a 1. 2
11, 241, 1231, 71421281, 2468101, 246810121, 244872961201441681, 8162432404856641, 1234567891, 10320630941251561872182492710301, 12345678910111, 12243648607284961081201321441, 43861291722152583013443874304735165591, 9418828237647056465875284694010341128122213161, 214263841051261471681892102312522732943151 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..187

EXAMPLE

a(3) = 1231 and k = 1.

MAPLE

dcat:= proc(L) local t, i;

t:= L[1];

for i from 2 to nops(L) do

t:= t*10^(1+ilog10(L[i]))+L[i]

od:

t

end proc:

f:= proc(n) local r, k, p;

for k from 1 do

p:= dcat([seq(r*k, r=1..n), 1]);

if isprime(p) then return p fi

od

end proc:

map(f, [$1..20]); # Robert Israel, Apr 30 2018

CROSSREFS

Cf. A089329.

Sequence in context: A296170 A264465 A090921 * A077422 A267642 A267665

Adjacent sequences: A089325 A089326 A089327 * A089329 A089330 A089331

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Nov 04 2003

EXTENSIONS

More terms from David Wasserman, Sep 13 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 1 03:09 EST 2022. Contains 358454 sequences. (Running on oeis4.)