Regex match line starting with whitespace and first character is non-digit - regex

Question

I am trying to create a regex that will only match lines that start with whitespace, then have 1-4 non-digits as the first characters, and then at least one or more spaces after the digits. The purpose of this regex is to use it in the "Find and Replace" option of Notepad++ to remove any lines that do not start with space(s) and then have a number as the first character in the line.
What I have now is allowing me to match the lines that start with whitespace and are followed with a group of digits and another space. However, these are the lines I want to keep. How can I modify the following regex so that it will match everything else other than these lines?
/^([\s]+\d[\s]|[\s]+\d\d[\s]|[\s]+\d\d\d[\s])/gm
Here's an example of the data we're using the regex on. The regex should only match the lines that DO NOT start with 1, 2, 49, 50, 99 and 100. Note that the lines that start with "40th" and "5/23/2017" should match.
Page 1
40th Marathon and 25th Marathon Relay
5/23/2017 USATF Certified Marathon (#RE98723UB) Downtown/City, ST
Timing: Race Services See our Calendar of Events at www.website.com
Results questions: http://www.website.com/fixresults
=====================================================================================
**** FINAL RESULTS IN NETTIME ORDER ****
Place Div/Tot Div Halfway 22miles Guntime Nettime Pace Name
===== ======== ===== ======= ======= ======= ======= ===== =======
1 1/153 M0139 1:15:08 2:05:50 2:29:20 2:29:20 5:42 Eric
2 2/153 M0139 1:15:07 2:06:29 2:29:56* 2:29:56 5:44 Bryan
Record 2:17:35 by Randy in 1986
49 8/77 M4049 1:36:48 2:54:03 3:37:02 3:36:59 8:17 Joshua
50 28/153 M0139 1:49:45 3:03:56 3:37:38# 3:37:22 8:18 Brian
# Under USATF OPEN guideline
99 1/16 M6069 1:56:30 3:15:24 3:51:06 3:50:46 8:49 Paul
100 3/35 F5059 1:50:06 3:11:37 3:51:03 3:50:47 8:49 Ashley
101 4/35 F5059 1:55:26 3:16:37 3:56:03 3:55:57 9:14 Joan
* Under USATF Age-Group guideline
% For an Explanation of AgeGraded Percentages, See Here: http://www.website.com/agegrading
So if we used the regex in Notepad++ to find the matching strings/lines and replace (delete) them, the desired end result would be as follows (in other words, the following lines would NOT match the regex):
1 1/153 M0139 1:15:08 2:05:50 2:29:20 2:29:20 5:42 Eric
2 2/153 M0139 1:15:07 2:06:29 2:29:56* 2:29:56 5:44 Bryan
49 8/77 M4049 1:36:48 2:54:03 3:37:02 3:36:59 8:17 Joshua
50 28/153 M0139 1:49:45 3:03:56 3:37:38# 3:37:22 8:18 Brian
99 1/16 M6069 1:56:30 3:15:24 3:51:06 3:50:46 8:49 Paul
100 3/35 F5059 1:50:06 3:11:37 3:51:03 3:50:47 8:49 Ashley
101 4/35 F5059 1:55:26 3:16:37 3:56:03 3:55:57 9:14 Joan
Any assistance would be greatly appreciated.

Answer 1

See regex in use here
^(?! +\d+ ).*\n*
^ Assert position at the start of the line
(?! +\d+ ) Negative lookahead ensuring what follows is not one or more spaces, then one or more digits, then a space
.* Match any character (except \n) any number of times
\n* Matches any number of newline characters
Result:
1 1/153 M0139 1:15:08 2:05:50 2:29:20 2:29:20 5:42 Eric
2 2/153 M0139 1:15:07 2:06:29 2:29:56* 2:29:56 5:44 Bryan
49 8/77 M4049 1:36:48 2:54:03 3:37:02 3:36:59 8:17 Joshua
50 28/153 M0139 1:49:45 3:03:56 3:37:38# 3:37:22 8:18 Brian
99 1/16 M6069 1:56:30 3:15:24 3:51:06 3:50:46 8:49 Paul
100 3/35 F5059 1:50:06 3:11:37 3:51:03 3:50:47 8:49 Ashley
101 4/35 F5059 1:55:26 3:16:37 3:56:03 3:55:57 9:14 Joan

Answer 2

If this is to use in the Find/Replace dialog then you can use a cunning trick...
^(pattern_I_want_to_keep)$|^.*$
And replace it with
\1
Anything that doesn't match what you want to keep will be removed, although it will leave a blank line. They can be removed with a plugin or another regex.
This is simpler to read than concocting a match for what you don't want to keep, or using a negative lookahead.