Information on mass chains and nuclides available on this website:

WWW TUNL

¹⁵Be has not been observed. The calculated mass excess is 51.18 MeV: see (81AJ01). It is calculated to be particle unstable with respect to decay into ¹⁴Be + n by 2.42 MeV. The binding energy of ¹³Be + 2n is +0.31 MeV. See also (SE81C, AN83D; theor.).