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A068697 Smallest prime which is a concatenation of n consecutive odd numbers. If no such prime exists then 0. 0
3, 13, 0, 23252729, 2527293133, 0, 57911131517, 4547495153555759, 0, 135791113151719, 87899193959799101103105107, 0, 23252729313335373941434547, 357911131517192123252729, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(3k) = 0.

LINKS

Table of n, a(n) for n=1..15.

EXAMPLE

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.

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 *)

CROSSREFS

Cf. A052077.

Sequence in context: A167368 A318165 A215240 * A010258 A107774 A253685

Adjacent sequences:  A068694 A068695 A068696 * A068698 A068699 A068700

KEYWORD

base,hard,nonn

AUTHOR

Amarnath Murthy, Mar 03 2002

EXTENSIONS

More terms from Sascha Kurz, Mar 26 2002

STATUS

approved

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Last modified December 7 20:40 EST 2021. Contains 349589 sequences. (Running on oeis4.)