"series of digits" is a correct and usable phrase in written English.
It refers to a set or sequence of numbers, typically written in numerical form. You can use it in situations where you need to describe the specific sequence or arrangement of numbers. Example: The password for the online banking account must be at least 8 characters long and include a series of digits. (In this sentence, "series of digits" refers to a consecutive set of numbers, rather than specific numbers.).
He handed her a slip of paper bearing a series of digits and numerals and obscure typographical symbols.
The system reads a series of digits, which the advertiser types into a Web page as verification before the ad will appear on the site.
Punching in a series of digits, he showed me the screen and what was clearly the fee the Thai mafia required for playing on their dock.
The hunt came to an end on a footbridge above the F.D.R. Drive, where a series of digits, illuminated by glow sticks, spelled out a cell-phone number.
"Because the series of digits is randomly presented, people don't know when the 3 is going to be presented," he said.
In the digit span task, children listened to a series of digits read aloud by the experimenter and were asked to repeat the sequence.
Subjects were required to monitor a series of single digits (0 9) appearing on the screen at a rate of 100 digits every minute and respond to consecutive sequences of three odd or even digits using a mouse button during the 9-min test period.
The Digit Triplets test (Smits & Houtgast 2004; Smits et al. 2005) presented series of three digits (monosyllables 0 to 9) against steady, speech-shaped background noise.
The structure of a molecule is encoded in a series of binary digits (bits) that represent the presence or absence of particular substructures in the molecule.
The amplitude at each interval is quantized, or assigned a value, and the values are mapped into a series of binary digits, or bits.
In the test, participants view a computer monitor on which a random series of single digits are presented at the regular rate of 1 per 1.15 seconds.
