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%I #9 Jan 12 2016 16:22:13
%S 0,11,218987,55844736,8299697699240,2585386023324464
%N Numbers k such that k+x+y is a square and k+u+v is a triangular number, where x and y are the two squares nearest to k, while u and v are the two triangular numbers nearest to k.
%C Intersection of A239071 and A238489.
%e 11 is in the sequence because the two squares nearest to 11 are 9 and 16 and 11+9+16=36 is a square, and also the two triangular numbers nearest to 11 are 10 and 15, and 11+10+15=36 is a triangular number.
%e Similarly, 218987 is in the sequence because 218987+467^2+468^2=656100 is a square, and 218987+triangular(661)+triangular(662)=657231 is a triangular number.
%Y Cf. A000217, A000290, A238489, A239071.
%K nonn,hard,more
%O 1,2
%A _Alex Ratushnyak_, Mar 12 2014
%E a(5)-a(6) from _Lars Blomberg_, Jan 12 2016
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