A068697 Smallest prime which is a concatenation of n consecutive odd numbers. If no such prime exists then 0.

3, 13, 0, 23252729, 2527293133, 0, 57911131517, 4547495153555759, 0, 135791113151719, 87899193959799101103105107, 0, 23252729313335373941434547, 357911131517192123252729, 0

Offset: 1

Author

Amarnath Murthy, Mar 03 2002

Keywords

• base
• nonn

Comments

a(3k) = 0.

Examples

			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.
		

Links

• Sean A. Irvine, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A052077.

Programs

Mathematica

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 *)

Extensions

More terms from Sascha Kurz, Mar 26 2002