These two procedures let me reset the sequence and reset the sequence based on data in a table (apologies for the coding conventions used by this client):
CREATE OR REPLACE PROCEDURE SET_SEQ_TO(p_name IN VARCHAR2, p_val IN NUMBER)
AS
l_num NUMBER;
BEGIN
EXECUTE IMMEDIATE 'select ' || p_name || '.nextval from dual' INTO l_num;
-- Added check for 0 to avoid "ORA-04002: INCREMENT must be a non-zero integer"
IF (p_val - l_num - 1) != 0
THEN
EXECUTE IMMEDIATE 'alter sequence ' || p_name || ' increment by ' || (p_val - l_num - 1) || ' minvalue 0';
END IF;
EXECUTE IMMEDIATE 'select ' || p_name || '.nextval from dual' INTO l_num;
EXECUTE IMMEDIATE 'alter sequence ' || p_name || ' increment by 1 ';
DBMS_OUTPUT.put_line('Sequence ' || p_name || ' is now at ' || p_val);
END;
CREATE OR REPLACE PROCEDURE SET_SEQ_TO_DATA(seq_name IN VARCHAR2, table_name IN VARCHAR2, col_name IN VARCHAR2)
AS
nextnum NUMBER;
BEGIN
EXECUTE IMMEDIATE 'SELECT MAX(' || col_name || ') + 1 AS n FROM ' || table_name INTO nextnum;
SET_SEQ_TO(seq_name, nextnum);
END;