/**
 * Triple Exponential Moving Average (TEMA).
 * Combines three nested EMAs to reduce lag while smoothing:
 * TEMA = 3*EMA1 - 3*EMA2 + EMA3. Preserves NaN gaps and seeds
 * each EMA before emitting values.
 * @param source Input series
 * @param period Smoothing period (must be > 0)
 * @returns Float64Array of TEMA values (NaN where undefined)
 */
export declare function tema(source: ArrayLike<number>, period: number): Float64Array;