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 A084960 #24 May 30 2025 08:03:10
%S A084960 2,3,5,83,263,5333,5333,6714497,42360737,3757699889,3757699889,
%T A084960 1431898413161,5654774136689,12756824771254199,184574272412533499
%N A084960 Initial prime of a prime chain of length n under the iteration x->5x+4.
%C A084960 This is a special case of prime chains generated by f(x) = c*x + d.
%H A084960 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 A084960 a(3) = 5 since 5, f(5) = 29 and f(29) = 149 are primes when f(x) = 5x+4.
%t A084960 t[p_] := Block[{c=1, q = 5*p+4}, While[ PrimeQ@q, q = 5*q + 4; c++]; c]; a[n_] := Block[{p = 2}, While[t[p] < n, p = NextPrime@ p]; p]; Array[a, 8] (* _Giovanni Resta_, Mar 21 2017 *)
%Y A084960 Cf. A057330, A057331, A083388, A084954, A084955, A084956, A084957, A084958, A084959, A084961.
%K A084960 nonn,hard,more
%O A084960 1,1
%A A084960 _W. Edwin Clark_, Jun 14 2003
%E A084960 a(9) from _Stefan Steinerberger_, May 18 2007
%E A084960 a(10)-a(11) from _Donovan Johnson_, Sep 27 2008
%E A084960 a(12)-a(13) from _Giovanni Resta_, Mar 21 2017
%E A084960 a(14)-a(15) from _Bert Dobbelaere_, May 30 2025