The 15-theorem asserts that a positive definite integral quadratic form represents all numbers iff it represents the numbers in this sequence. "Integral" here means that the quadratic form equals x^T M x, where x is an integer vector and M is an integer matrix. - T. D. Noe, Mar 30 2006
Manjul Bhargava, On the Conway-Schneeberger fifteen theorem, Contemporary Mathematics 272 (1999), 27-37.
J. H. Conway, The Sensual (Quadratic) Form, M.A.A., 1997, p. 141.
J. H. Conway, Universal quadratic forms and the fifteen theorem, Contemporary Mathematics 272 (1999), 23-26.
J. H. Conway and W. A. Schneeberger, personal communication.