1,1

There are infinitely many terms (see A214937 for a proof)

Ivan N. Ianakiev, Table of n, a(n) for n = 1..1000

a(n) = sqrt(A214937(n))

2 and 7 are in the sequence because 2^2=1^2+2*3/2 and 7^2=2^2+9*10/2

Cf. A000217, A000290, A214937

Sequence in context: A074232 A007417 A039099 * A035257 A235331 A175969

Adjacent sequences: A215066 A215067 A215068 * A215070 A215071 A215072

nonn

Ivan N. Ianakiev, Aug 02 2012

approved