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Sum of prime-length repunits: Sum_{k=1..n} r(prime(k)), where r()=A002275.
1

%I #13 Jul 17 2022 09:21:30

%S 0,11,122,11233,1122344,11112233455,1122223344566,11112233334455677,

%T 1122223344445566788,11112233334455556677899,

%U 11111122223344445566667789010,1122222233334455556677778900121

%N Sum of prime-length repunits: Sum_{k=1..n} r(prime(k)), where r()=A002275.

%e a(3)=11233 because 11 + 111 + 11111 = 11233.

%o (PARI) a(n) = sum(k=1, n, (10^prime(k)-1)/9); \\ _Michel Marcus_, Jul 17 2022

%Y Cf. A097709.

%Y Partial sums of A031974.

%K base,nonn

%O 0,2

%A _Jason Earls_, Aug 21 2004