Here is something that might be worth trying. Set a stop watch and see how long it takes you to find all occurrences of the number "4"
The length of time taken is one measure of concentration. Use a pencil to cross out each number.
You might need to download and delete spaces to have one large array.
Now smoke a cigarette and repeat. Does smoking affect your concentration?
Have a beer.
Play loud music.
If you use some method to train your concentration, use this chart to test yourself a week later.
A week later find all occurences of the number "5".
Random digits from
http://www.rand.org/pubs/monograph_reports/MR1418/index2.html have been repeated a few times for a large chart.
50134916495151094993505550804986497475565065501450345057490250614942494649605019500950534966489150314895503750625170488650334982518050744892499250115005495948724976499349325039496550344943493251165070501151524990504749745107486949255023490250035092516349365020506949144943491449464860489951384959508950475030503950024937499849574964512449094995505349464995505949485048504150775051500450244886491750044958499350644987504149844991498751134882496849615029503850225023501049884936502551104923502549755095505150354962494248825094496249454891501450025038502351794852495750355051502150364927502249884910505350
50884989504249484999502850374893500449724970503449965008504950164954498949705014164953
50134916495151094993505550804986497475565065501450345057490250614942494649605019500950534966489150314895503750625170488650334982518050744892499250115005495948724976499349325039496550344943493251165070501151524990504749745107486949255023490250035092516349365020506949144943491449464860489951384959508950475030503950024937499849574964512449094995505349464995505949485048504150775051500450244886491750044958499350644987504149844991498751134882496849615029503850225023501049884936502551104923502549755095505150354962494248825094496249454891501450025038502351794852495750355051502150364927502249884910505350
5088498950424948499950285037489350044972497050344996500850495016495449894970501416495350134916495151094993505550804986497475565065501450345057490250614942494649605019500950534966489150314895503750625170488650334982518050744892499250115005495948724976499349325039496550344943493251165070501151524990504749745107486949255023490250035092516349365020506949144943491449464860489951384959508950475030503950024937499849574964512449094995505349464995505949485048504150775051500450244886491750044958499350644987504149844991498751134882496849615029503850225023501049884936502551104923502549755095505150354962494248825094496249454891501450025038502351794852495750355051502150364927502249884910505350
50884989504249484999502850374893500449724970503449965008504950164954498949705014164953
50134916495151094993505550804986497475565065501450345057490250614942494649605019500950534966489150314895503750625170488650334982518050744892499250115005495948724976499349325039496550344943493251165070501151524990504749745107486949255023490250035092516349365020506949144943491449464860489951384959508950475030503950024937499849574964512449094995505349464995505949485048504150775051500450244886491750044958499350644987504149844991498751134882496849615029503850225023501049884936502551104923502549755095505150354962494248825094496249454891501450025038502351794852495750355051502150364927502249884910505350
50884989504249484999502850374893500449724970503449965008504950164954498949705014164953
50134916495151094993505550804986497475565065501450345057490250614942494649605019500950534966489150314895503750625170488650334982518050744892499250115005495948724976499349325039496550344943493251165070501151524990504749745107486949255023490250035092516349365020506949144943491449464860489951384959508950475030503950024937499849574964512449094995505349464995505949485048504150775051500450244886491750044958499350644987504149844991498751134882496849615029503850225023501049884936502551104923502549755095505150354962494248825094496249454891501450025038502351794852495750355051502150364927502249884910505350
50884989504249484999502850374893500449724970503449965008504950164954498949705014164953
Frequency count for the digits
0 529
1 225
2 200
3 200
4 605
5 620
6 165
7 140
8 225
9 540
Double the chart and double the frequency count as needed.