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
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
Programs
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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
Comments