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a[n] is the largest prime before A002276[n] repdigits.
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%I #6 Dec 19 2020 17:37:54

%S 19,211,2221,22193,222199,2222219,22222199,222222193,2222222137,

%T 22222222189,222222222169,2222222222197,22222222222201,

%U 222222222222151,2222222222222203,22222222222222153,222222222222222221

%N a[n] is the largest prime before A002276[n] repdigits.

%e n=2: 19 is before 22.

%t <<NumberTheory`NumberTheoryFunctions` Table[Table[PreviousPrime[ *2(10^n-1)/9], {n, 2, 35}]

%t Drop[NextPrime[#,-1]&/@LinearRecurrence[{11,-10},{0,2},20],2] (* _Harvey P. Dale_, Dec 19 2020 *)

%Y Cf. A003618, A003617, A096497, A096498, A068104, A002275-A002283, A099656-A099669.

%K base,nonn

%O 2,1

%A _Labos Elemer_, Nov 17 2004