login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A275542 The digits of the integers with the nonprimes removed. 2
2, 3, 5, 7, 2, 3, 5, 7, 2, 2, 2, 2, 2, 3, 2, 2, 5, 2, 2, 7, 2, 2, 3, 3, 3, 2, 3, 3, 3, 3, 5, 3, 3, 7, 3, 3, 2, 3, 5, 7, 5, 5, 5, 2, 5, 3, 5, 5, 5, 5, 5, 7, 5, 5, 2, 3, 5, 7, 7, 7, 7, 2, 7, 3, 7, 7, 5, 7, 7, 7, 7, 7, 2, 3, 5, 7, 2, 3, 5, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Write the digits of the positive integers one by one: 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 0, 1, 1, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 8, 1, 9, 2, 0, 2, 1, etc. (this is A007376). Then from that sequence, remove the nonprimes, leaving a sequence that consists entirely of 2s, 3s, 5s and 7s.
LINKS
Metin Sariyar, Table of n, a(n) for n = 1..32000 (terms 1..2401 from Robert Price)
EXAMPLE
From the single-digit numbers, we obviously get the first four terms of this sequence: 2, 3, 5, 7.
10 is composite and neither of its digits is a single-digit prime, so it contributes nothing to this sequence.
11 is prime but its digits consist of two 1s, so like 10 it also contributes nothing to the sequence.
12 is composite, but its least significant digit is 2, which is a prime, and thus 12 contributes a 2 to the sequence.
MATHEMATICA
Flatten[Table[Select[IntegerDigits[n], PrimeQ], {n, 100}]] (* Alonso del Arte, Aug 01 2016 *)
CROSSREFS
Sequence in context: A093338 A229875 A230199 * A187559 A104212 A139751
KEYWORD
nonn,base
AUTHOR
Dave Durgin, Aug 01 2016
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 16:12 EDT 2024. Contains 371254 sequences. (Running on oeis4.)