This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A097708 #13 Jul 17 2022 09:21:30
%S A097708 0,11,122,11233,1122344,11112233455,1122223344566,11112233334455677,
%T A097708 1122223344445566788,11112233334455556677899,
%U A097708 11111122223344445566667789010,1122222233334455556677778900121
%N A097708 Sum of prime-length repunits: Sum_{k=1..n} r(prime(k)), where r()=A002275.
%e A097708 a(3)=11233 because 11 + 111 + 11111 = 11233.
%o A097708 (PARI) a(n) = sum(k=1, n, (10^prime(k)-1)/9); \\ _Michel Marcus_, Jul 17 2022
%Y A097708 Cf. A097709.
%Y A097708 Partial sums of A031974.
%K A097708 base,nonn
%O A097708 0,2
%A A097708 _Jason Earls_, Aug 21 2004