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A032721 n prefixed by '4' and followed by '7' is a prime. 1

%I #8 Jan 08 2019 20:28:15

%S 5,6,8,12,15,17,21,29,32,33,35,39,44,45,50,51,54,56,59,63,65,78,81,87,

%T 93,95,96,98,101,104,105,107,111,117,122,125,135,138,146,150,159,161,

%U 162,164,168,173,177,188,189,192,194,195,201,215,218,219,222,225

%N n prefixed by '4' and followed by '7' is a prime.

%H Harvey P. Dale, <a href="/A032721/b032721.txt">Table of n, a(n) for n = 0..1000</a>

%t Select[Range[300],PrimeQ[FromDigits[Join[{4},IntegerDigits[#],{7}]]]&] (* _Harvey P. Dale_, Jan 08 2019 *)

%K nonn,base

%O 0,1

%A _Patrick De Geest_, May 15 1998

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Last modified May 28 12:36 EDT 2024. Contains 372913 sequences. (Running on oeis4.)