A073176 First n-digit prime in the concatenation of odd integers allowing leading zeros.

3, 13, 911, 5791, 79111, 31051, 1232527, 23252729, 113151719, 2527293133, 57911131517, 991011031051, 6769717375777, 13579111315171, 135791113151719, 4547495153555759, 31517192123252729, 719212325272931333, 1131517192123252729, 71921232527293133353

Offset: 1

Author

Zak Seidov, Aug 22 2002

Keywords

• easy
• nonn
• base

Comments

Leading zeros count but are not printed (cf. A073428).

Examples

			a(4) = 5791 because first 4-digit prime in 135791113151719212325272931333537394143454749... is 5791. Notice that a(6) = 31051 because actually it is 031051, If we remove initial zeros, then a(6) = 105107.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..996

Crossrefs

Cf. A005408, A073062, A073175, A073428.

Programs

Maple

S:= "":
for i from 1 to 300 by 2 do
  S:= cat(S,sprintf("%d",i))
od:
nS:= length(S):
for n from 1 do
  found:= false;
  for i from 1 to nS-n+1 do
    x:= parse(S[i..n+i-1]);
    if isprime(x) then R[n]:= x; found:= true; break fi
  od;
  if not found then break fi;
od:
seq(R[i],i=1..n-1); # Robert Israel, Nov 27 2024

Extensions

Data corrected by Sean A. Irvine, Nov 20 2024

Name modified by Sean A. Irvine, Jan 31 2025