import { Observable } from 'rxjs';
export declare function scan<T, R>(this: Observable<T>, accumulator: (acc: R, value: T, index: number) => R, seed: R): Observable<R>;
export declare function scan<T>(this: Observable<T>, accumulator: (acc: T, value: T, index: number) => T, seed?: T): Observable<T>;
export declare function scan<T, R>(this: Observable<T>, accumulator: (acc: R, value: T, index: number) => R): Observable<R>;