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Smallest prime starting with 1 and followed by a string of n 0's.
2

%I #9 Aug 07 2021 13:24:23

%S 101,1009,10007,100003,1000003,100000037,100000007,1000000007,

%T 100000000019,100000000003,10000000000037,100000000000031,

%U 1000000000000037,10000000000000061,100000000000000013

%N Smallest prime starting with 1 and followed by a string of n 0's.

%C Not the same as A139535 though most entries match. (First dissimilarity occurs for n=19: A139535(19)=1000000000000000000409; A139536(19)=10000000000000000000139.)

%H Harvey P. Dale, <a href="/A139536/b139536.txt">Table of n, a(n) for n = 1..997</a>

%t Table[Module[{k=1},While[CompositeQ[10^IntegerLength[k] FromDigits[ PadRight[ {1},n,0]]+k],k+=2];10^IntegerLength[k] FromDigits[ PadRight[ {1},n,0]]+k],{n,2,20}] (* _Harvey P. Dale_, Aug 07 2021 *)

%K nonn,base

%O 1,1

%A _Lekraj Beedassy_, Apr 25 2008