A series of numbers in regular order: 1, 2, 4, 7, 11, 16, 22, 29 The number 1997 of this string is______ .

A series of numbers in regular order: 1, 2, 4, 7, 11, 16, 22, 29 The number 1997 of this string is______ .

1+1+2+3+4+5+… +1995 + 1996 = 1 + (1 + 1996) × (1996 △ 2) = 1 + 1997 × 998 = 1 + 1993006 = 1993007 answer: the 1997 number of this series is 1993007. So the answer is: 1993007