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 A084958 #16 Feb 04 2020 06:35:07
%S A084958 2,3,13,19,373,135859,135859,18235423,26588257,93112729,376038903103,
%T A084958 7087694466289,120223669028389
%N A084958 Initial prime of a prime chain of length n under the iteration x->5x+2.
%C A084958 This is a special case of prime chains generated by f(x) = cx + d.
%C A084958 a(11) > 8695354111. - _Donovan Johnson_, Sep 27 2008
%H A084958 D. H. Lehmer, <a href="https://doi.org/10.1112/plms/s3-14A.1.183">On certain chains of primes</a>, Proc. London Math. Soc. (3) 14a 1965 183-186.
%e A084958 a(3)=13 since 13, f(13)=67 and f(67)=337 are primes when f(x) = 5x+2.
%t A084958 c[p_] := Block[{k = 1, q = 5*p+2}, While[ PrimeQ[q], q = 5*q+2; k++]; k]; a[n_] := Block[{p = 2}, While[c[p] < n, p = NextPrime@ p]; p]; Array[a, 7] (* _Giovanni Resta_, Mar 21 2017 *)
%Y A084958 Cf. A057330, A057331, A083388, A084954, A084955, A084956, A084957, A084959, A084960, A084961.
%K A084958 more,nonn
%O A084958 1,1
%A A084958 _W. Edwin Clark_, Jun 14 2003
%E A084958 a(10) from _Donovan Johnson_, Sep 27 2008
%E A084958 a(11)-a(12) from _John Cerkan_, Jan 20 2017
%E A084958 a(13) from _Giovanni Resta_, Mar 21 2017