Z
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zag number
PL alternating permutation .
zero
Denoted 0. (1) As placeholder in basal notation (PL), e.g., decimal; thus, 5207 is thereby distinguished from 527
. (2)As initator of counting (a.k.a. natural) number system (PL) by recursion (PL). Originated in arithmetic of India by at least 650 AD. Disseminated by Islamic mathematication, hence, "Hindu-Arabic notation" (PL).
zig number
PL alternating permutation .
zigzag number, Euler's
PL alternating permutation.