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 A140793 Smallest prime which is the concatenation of 2 or more consecutive numbers starting with n, or -1 if no such prime exists. 5
 23, 345678910111213141516171819, 4567, 567891011121314151617, 67, 78910111213, 89 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS Comment from Ray G. Opao, Sep 30 2008: a(9) is the following number: 91011121314151617181920212223242526272829303132333435363738394041424 34445464748495051525354555657585960616263646566676869707172737475767 77879808182838485868788899091929394959697989910010110210310410510610 71081091101111121131141151161171181191201211221231241251261271281291 30131132133134135136137138139140141142143144145146147148149150151152 15315415515615715815916016116216316416516616716816917017117217317417 5176177178179180181182183184185186187. LINKS FORMULA a(n) = concatenate( n, ..., A084559(n)). - M. F. Hasler, Feb 22 2021 MATHEMATICA f[n_] := Block[{c = n, k = n + 1}, While[c = 10^IntegerLength[k] c + k; p = c; !PrimeQ[c], k++]; c]; Table[f[n], {n, 2, 8}] (* Robert G. Wilson v, Jun 24 2012 *) pr[n_]:=Module[{k=1}, While[!PrimeQ[FromDigits[Flatten[IntegerDigits/@Range[n, n+k]]]], k++]; FromDigits[Flatten[IntegerDigits/@Range[n, n+k]]]]; Array[pr, 8, 2] (* Harvey P. Dale, Mar 14 2014 *) PROG (PARI) A140793(n, N=n, T=10^logint(n, 10))=while(T*=10, for(m=n+1, n=T-1, ispseudoprime(N=N*T+m)&&return(N))) \\ M. F. Hasler, Feb 22 2021 CROSSREFS Cf. A341715, A341716, A341717. Sequence in context: A030464 A180731 A053558 * A023923 A267334 A202184 Adjacent sequences:  A140790 A140791 A140792 * A140794 A140795 A140796 KEYWORD nonn,base,more AUTHOR Lekraj Beedassy, Jul 15 2008 EXTENSIONS Added escape clause to definition. - N. J. A. Sloane, Feb 22 2021 STATUS approved

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Last modified August 1 12:15 EDT 2021. Contains 346385 sequences. (Running on oeis4.)