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A104914 Numbers n such that the string 987654321k is prime. 8

%I #14 Sep 08 2022 08:45:17

%S 1,7,37,67,77,91,109,113,133,193,197,223,317,319,331,347,371,397,403,

%T 449,491,529,569,571,587,611,623,649,673,737,743,757,767,769,851,883,

%U 893,917,919,931,989,991,1001,1019,1021,1033,1081,1091,1121,1127,1141

%N Numbers n such that the string 987654321k is prime.

%H Michael De Vlieger, <a href="/A104914/b104914.txt">Table of n, a(n) for n = 1..10000</a>

%t With[{r = Reverse@ Range@ 9}, Select[Range[1200], PrimeQ[FromDigits[r ~Join~ IntegerDigits@ #]] &]] (* _Michael De Vlieger_, Jan 20 2018 *)

%t Select[Range[1200],PrimeQ[987654321*10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, Jul 31 2018 *)

%o (Magma) [ n: n in [1..1750] | IsPrime(Seqint(Intseq(n) cat [1, 2, 3, 4, 5, 6, 7, 8, 9])) ]; // _Vincenzo Librandi_, Feb 02 2011

%Y Cf. A104915.

%K nonn,base

%O 1,2

%A _Zak Seidov_, Mar 29 2005

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Last modified July 13 14:24 EDT 2024. Contains 374284 sequences. (Running on oeis4.)