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A089338 Beginning with 3 the smallest number such that the concatenation a(n), a(n-1), ... a(2), a(1) is a prime. 1

%I #10 Jan 17 2022 14:46:34

%S 3,1,1,2,1,6,11,16,11,1,8,21,13,11,34,41,12,4,66,24,15,17,4,122,70,96,

%T 33,2,43,5,3,100,44,28,23,27,12,4,113,10,3,90,9,162,15,9,69,146,9,145,

%U 74,3,42,99,31,93,35,259,53,79,14,285,84,1,36,78,147,78,66,246,155,624

%N Beginning with 3 the smallest number such that the concatenation a(n), a(n-1), ... a(2), a(1) is a prime.

%H Harvey P. Dale, <a href="/A089338/b089338.txt">Table of n, a(n) for n = 0..200</a>

%e 3, 13, 113, 2113, 12113, 612113, ...etc. are primes.

%t nxt[{cnc_,a_}]:=Module[{k=1},While[!PrimeQ[k*10^IntegerLength[ cnc]+ cnc],k++];{k*10^IntegerLength[cnc]+cnc,k}]; NestList[nxt,{3,3},80][[All,2]] (* _Harvey P. Dale_, Jan 17 2022 *)

%K base,nonn

%O 0,1

%A _Amarnath Murthy_, Nov 04 2003

%E More terms from _Ray Chandler_, Nov 07 2003

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)