A089328 Smallest prime of the form the concatenation r*k for r = 1 to n followed by a 1.

11, 241, 1231, 71421281, 2468101, 246810121, 244872961201441681, 8162432404856641, 1234567891, 10320630941251561872182492710301, 12345678910111, 12243648607284961081201321441, 43861291722152583013443874304735165591, 9418828237647056465875284694010341128122213161, 214263841051261471681892102312522732943151

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 A361143 A267642

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