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 A087146 #16 Dec 11 2024 21:13:58
%S A087146 1,2,3,5,9,13,14,17,27,28,33,39,103,115,205,291,1431,1532,1710,1937,
%T A087146 3901,3981,4682,6569,20266,20662
%N A087146 Numbers k such that k! + (k+1)! - 1 is prime.
%C A087146 291 is in the sequence and also is in the sequence A087147, thus (291!+292!-1,291!+292!+1) is a twin pair of primes. Any additional terms are greater than 1800 with the next prime having more than 5086 digits.
%C A087146 a(27) > 25000. - _Robert Price_, Jul 12 2015
%C A087146 a(1)-a(26) give certified primes. - _Robert Price_, Jul 12 2015
%D A087146 H. Dubner, Factorial and primorial primes, J. Rec. Math., 19(No. 3, 1987)
%e A087146 3 is in the sequence because 3!+4!-1=29 is prime.
%t A087146 v={}; Do[If[PrimeQ[n!+(n+1)!-1], v=Append[v, n]; Print[v]], {n, 1800}]; v
%Y A087146 Cf. A087147, A051856, A125174 (corresponding primes).
%K A087146 nonn
%O A087146 1,2
%A A087146 _Farideh Firoozbakht_, Aug 19 2003
%E A087146 One more term from _Ryan Propper_, Aug 13 2005
%E A087146 a(21)-a(26) from _Robert Price_, Jul 12 2015