Every sedenion is a real linear combination of the unit sedenions 1, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11, e12, e13, e14 and e15, which form a basis of the vector space of sedenions.
The sedenions have a multiplicative identity element 1 and multiplicative inverses, but they are not a division algebra. This is because they have zero divisors; this means that two non-zero numbers can be multiplied to obtain a zero result: a trivial example is (e3 + e10)×(e6 − e15). All hypercomplex number systems based on the Cayley-Dickson construction from sedenions on contain zero divisors.
Imaeda, K., Imaeda, M.: Sedenions: algebra and analysis, Applied Mathematics and Computation, 115:77-88 (2000)
Kinyon, M.K., Phillips, J.D., Vojtěchovský, P.: C-loops: Extensions and constructions, Journal of Algebra and its Applications 6 (2007), no. 1, 1-20. [1]
Conic sedenions / "16-dim. M-algebra"
Arithmetic
In contrast to Cayley-Dickson sedenions, which are built on one and 15 roots of negative one, conic sedenions are built on 8 square roots each of positive and negative one. They share non-commutativity and non-associativity with Cayley-Dickson sedenion ("circular sedenion") arithmetic, however, conic sedenions are modular, alternative, and flexible. With the exception of its nilpotents, zero divisors, and zero itself, the arithmetic is closed with respect to the power-of and logarithm operations. Conic sedenions are not power-associative.
For detailed information and isomorphic subalgebras see Musean hypernumber.