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 A181920 #15 Aug 06 2025 22:36:05
%S A181920 1,2,25,90,456,608,1421,1469
%N A181920 Length of A185120(n): number of subsequent digits in the decimal expansion of e which form the next longer prime.
%C A181920 By definition, a strictly increasing sequence.
%C A181920 See A185120 for further comments and explanations.
%e A181920 The decimal expansion of e=exp(1)=2.718281828.... is split into
%e A181920 A185120(1) = 2 of length a(1)=1,
%e A181920 A185120(2) = 71 of length a(2)=2,
%e A181920 A185120(3) = 8281828459045235360287471 of length a(3)=25, etc.
%o A181920 (PARI) {default(realprecision,20000);e=exp(1)*.1; for( n=1,9e9, ispseudoprime(e\.1^n)||next; print1(n",");e=frac(e*10^n))}
%K A181920 nonn,base
%O A181920 1,2
%A A181920 _M. F. Hasler_, Apr 01 2012