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 A158191 Attach the smallest prime to the end of the string a(n-1) so a(n) is also prime 1
 2, 23, 233, 2333, 23333, 2333323, 23333237, 233332373, 23333237353, 2333323735319, 2333323735319149, 2333323735319149571, 23333237353191495713, 23333237353191495713131, 233332373531914957131313 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..200 EXAMPLE a(6)=2333323 since a(5)=23333 (prime) and 233333, 233335, 233337, 2333311, 2333313, 2333317 and 2333319 are all composite MATHEMATICA nxt[n_]:=Module[{k=3}, While[CompositeQ[n*10^IntegerLength[k]+k], k = NextPrime[ k]]; n*10^IntegerLength[k]+k]; NestList[nxt, 2, 20] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 13 2019 *) CROSSREFS Cf. A048549, A088603, A089703, A065712, A100893 Sequence in context: A127889 A088603 A048549 * A089703 A088094 A112782 Adjacent sequences:  A158188 A158189 A158190 * A158192 A158193 A158194 KEYWORD nonn,base AUTHOR Sergio Pimentel, Mar 13 2009 EXTENSIONS More terms from Sean A. Irvine, Nov 29 2009 STATUS approved

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Last modified September 19 21:11 EDT 2021. Contains 347564 sequences. (Running on oeis4.)