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Smallest prime which is a concatenation of n consecutive odd numbers. If no such prime exists then 0.
1

%I #12 Mar 04 2024 22:04:47

%S 3,13,0,23252729,2527293133,0,57911131517,4547495153555759,0,

%T 135791113151719,87899193959799101103105107,0,

%U 23252729313335373941434547,357911131517192123252729,0

%N Smallest prime which is a concatenation of n consecutive odd numbers. If no such prime exists then 0.

%C a(3k) = 0.

%H Sean A. Irvine, <a href="/A068697/b068697.txt">Table of n, a(n) for n = 1..100</a>

%e a(4) = 23252729 as a concatenation of 23,25,27 and 29. a(3) = 0 for a concatenation of 3 odd numbers is always a multiple of 3.

%t d[n_]:=IntegerDigits[n]; t={3}; Do[If[Mod[m,3]==0,x=0,k=1; While[!PrimeQ[x=FromDigits[Fold[Join,d[k],Table[d[k+2n],{n,m-1}]]]],k++]]; AppendTo[t,x],{m,2,15}]; t (* _Jayanta Basu_, May 21 2013 *)

%Y Cf. A052077.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Mar 03 2002

%E More terms from _Sascha Kurz_, Mar 26 2002