A term of a linear recurrence: fib(n), lucas(n), pell(n), jacobsthal(n), and the seed-generalised fib(n, a, b).
Indexing is the standard one: x(0) = 0, x(1) = 1, so fib(10) = 55, matching OEIS A000045 and every published table. The "classic rabbit" pair is fib(n, 1, 1), which is this sequence shifted by one (fib(n, 1, 1) = fib(n+1)). Stated here because it cannot be inferred and an off-by-one would be silent — the rule also applied to the spherical polar angle.
These are numeric sequences, not integer ones. The recurrence needs only addition and multiplication, so fib(5, 1.5, -pi) is a legitimate call and exact seeds stay exact. An exact integer index with exact seeds goes through linRecExact, which is what lets fib(79) be right: F(79) exceeds 2^53, so the Double path can only approximate it.
Value parameters
kind
which recurrence
n
the index
seeds
empty for the kind's own seeds, or exactly two expressions overriding them
