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 A162489 #11 Jul 26 2025 17:44:20
%S A162489 2,2,2,2,5,15,2,33,7,3,21,8,34,9,80,56,67,9,32,65,45,133,98,36,51,157,
%T A162489 76,214,200,87,91,111,122,342,20,142,364,289,9,184,98,423,365,20,56,
%U A162489 441,329,8,234,234,157,291,91,379,98,464,518,325,32,654,87,634,34,21,443
%N A162489 Least y such that x^y + y^x is prime, for x = A162488(n).
%C A162489 Sequences A162488 and A162490 list the corresponding x values and primes.
%C A162489 See there and the main entry A094133 for more information, links and references.
%F A162489 a(n)^A162488(n)+A162488(n)^a(n) = A162490(n)
%e A162489 The least x such that x^y + y^x is prime for some x>y>1 is A162488(1)=3, the smallest such y is a(1)=2, yielding the prime A162490(1) = 9 + 8 = 17.
%t A162489 lst = {}; Do[ If[ PrimeQ[x^y + y^x], AppendTo[lst, {x, y}]], {x, 3, 750}, {y, 2, x - 1}]; Transpose[ lst][[2]] (* _Robert G. Wilson v_, Aug 17 2009 *)
%o A162489 (PARI) for(i=3,999,for(j=2,i-1,isprime(i^j+j^i)||next;print1(j", ");break))
%Y A162489 Cf. A094133, A162486, A162487, A162488, A162490.
%K A162489 nonn
%O A162489 1,1
%A A162489 _M. F. Hasler_, Jul 04 2009
%E A162489 More terms from _Robert G. Wilson v_, Aug 17 2009