cp's OEIS Frontend

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

%I A073176 #29 Jan 31 2025 17:31:34
%S A073176 3,13,911,5791,79111,31051,1232527,23252729,113151719,2527293133,
%T A073176 57911131517,991011031051,6769717375777,13579111315171,
%U A073176 135791113151719,4547495153555759,31517192123252729,719212325272931333,1131517192123252729,71921232527293133353
%N A073176 First n-digit prime in the concatenation of odd integers allowing leading zeros.
%C A073176 Leading zeros count but are not printed (cf. A073428).
%H A073176 Robert Israel, <a href="/A073176/b073176.txt">Table of n, a(n) for n = 1..996</a>
%e A073176 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.
%p A073176 S:= "":
%p A073176 for i from 1 to 300 by 2 do
%p A073176   S:= cat(S,sprintf("%d",i))
%p A073176 od:
%p A073176 nS:= length(S):
%p A073176 for n from 1 do
%p A073176   found:= false;
%p A073176   for i from 1 to nS-n+1 do
%p A073176     x:= parse(S[i..n+i-1]);
%p A073176     if isprime(x) then R[n]:= x; found:= true; break fi
%p A073176   od;
%p A073176   if not found then break fi;
%p A073176 od:
%p A073176 seq(R[i],i=1..n-1); # _Robert Israel_, Nov 27 2024
%Y A073176 Cf. A005408, A073062, A073175, A073428.
%K A073176 easy,nonn,base
%O A073176 1,1
%A A073176 _Zak Seidov_, Aug 22 2002
%E A073176 Data corrected by _Sean A. Irvine_, Nov 20 2024
%E A073176 Name modified by _Sean A. Irvine_, Jan 31 2025