cp's OEIS Frontend

A080504 Triangle whose n-th row contains the least set (ordered lexicographically) of n distinct positive integers whose arithmetic and geometric means are both integers.

%I A080504 #7 Jun 06 2016 22:23:00
%S A080504 1,1,9,1,2,108,1,2,5,1000,1,2,3,4,1012500,1,2,3,4,8,15552,1,2,3,4,5,6,
%T A080504 25015118625000,1,2,3,4,5,6,11,17757684573750000,1,2,3,4,5,6,7,8,
%U A080504 19699405917187500,1,2,3,4,5,6,7,8,14,295491088757812500,1,2,3,4,5,6,7
%N A080504 Triangle whose n-th row contains the least set (ordered lexicographically) of n distinct positive integers whose arithmetic and geometric means are both integers.
%C A080504 Row n has the form {1,2,...,n-2,x,y} where n-1 <= x < y. x is minimal such that y exists.
%e A080504 The fourth row contains 1,2,5,1000, with AM=252 and GM=10. There is no set of the form {1,2,3,y} or {1,2,4,y} whose AM and GM are both integers.
%Y A080504 Cf. A080505, A081556, A080506, A080507, A080508, A080511.
%K A080504 nonn,tabl
%O A080504 1,3
%A A080504 _Amarnath Murthy_, Mar 20 2003