Syntax options:

    MINVALUE numeric-value | NOMINVALUE

    The MINVALUE clause specifies the minimum signed quadword
    (BIGINT) value that the sequence can generate. For an ascending
    sequence, the new minimum value must be less than or equal
    to the existing MINVALUE. For a descending sequence, the
    new minimum value must be less than or equal to the existing
    RDB$NEXT_SEQUENCE_VALUE. This prevents the minimum value
    from being greater than any currently issued values. In
    addition, the numeric value must be equal to or greater than -
    9223372036854775808. The MINVALUE must be less than the value
    specified with the MAXVALUE clause. The NOMINVALUE clause
    specifies that the minimum value for an ascending sequence is 1,
    and -9223372036854775808 (plus the cache size) for a descending
    sequence.

    The NOMINVALUE clause is the default.