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 A153431 #6 Jul 06 2022 10:08:47 %S A153431 1,1,1,4,28,28,170926,170926,931371868,15538734736,89468493268, %T A153431 6009549731752,89984938946056,43000687652274618 %N A153431 a(n) is the smallest number m such that all n+1 numbers m*10^k+1 k=0,1, ...,n are prime. %C A153431 If n<m and r=10^n*a(m)*a(n)-1 is prime then r has at least n+1 %C A153431 representations of the form p*q-(p+q)where p & q are prime. %C A153431 For n>3, 7 divides a(n). a(10) is greater than 4*10^10. %H A153431 Prime Puzzles <a href="http://www.primepuzzles.net/puzzles/puzz_482.htm">Two Bergot questions</a> %e A153431 28+1, 280+1, 2800+1, 28000+1, 280000+1 & 2800000+1 are prime and 28 is the smallest such number so a(5)=28. %Y A153431 Cf. A153432. %K A153431 nonn,more %O A153431 0,4 %A A153431 _Farideh Firoozbakht_, Mar 15 2009, Mar 27 2009 %E A153431 a(11)-a(13) from _Don Reble_, Jul 06 2022