A239203 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.

0, 11, 218987, 55844736, 8299697699240, 2585386023324464

Offset: 1

Author

Alex Ratushnyak, Mar 12 2014

Keywords

• nonn
• hard
• more

Comments

Intersection of A239071 and A238489.

Examples

			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.
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.
		

Crossrefs

Cf. A000217, A000290, A238489, A239071.

Extensions

a(5)-a(6) from Lars Blomberg, Jan 12 2016