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!)
A032437 Substrings from the right are prime numbers (using only odd digits different from 5). 12
3, 7, 13, 17, 37, 73, 97, 113, 137, 173, 197, 313, 317, 337, 373, 397, 773, 797, 937, 997, 1373, 1997, 3137, 3313, 3373, 3797, 7937, 9137, 9173, 9337, 9397, 13313, 33797, 39397, 79337, 79397, 91373, 91997, 99137, 99173, 99397, 139397, 379397 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Primes p with decimal expansion d_1 d_2 d_3 ... d_k such that the digits d_i are 1, 3, 7, or 9, and deleting 1, 2, 3, up to k-1 leading digits also produces a prime. For example, 9173 is a term because all of 9173, 173, 73, and 3 are primes. - N. J. A. Sloane, Jun 28 2022
LINKS
T. D. Noe, Table of n, a(n) for n = 1..58 [The complete list of terms]
C. Rivera, Prime strings
Eric Weisstein's World of Mathematics, Truncatable Prime.
EXAMPLE
173 is a term because 173, 73, and 3 are all primes. 371 is not a term because 371 and 1 are not primes. - N. J. A. Sloane, Jun 28 2022
MATHEMATICA
Select[Prime[Range[33000]], SubsetQ[{1, 3, 7, 9}, IntegerDigits[#]]&&AllTrue[Mod[#, 10^Range[ IntegerLength[ #]-1]], PrimeQ]&] (* Harvey P. Dale, Jun 28 2022 *)
PROG
(PARI) is(n)=my(d=digits(n)); for(i=1, n, if(!isprime(fromdigits(d[i..n])), return(0))); 1 \\ Charles R Greathouse IV, Jun 25 2017
CROSSREFS
Sequence in context: A113003 A045423 A214782 * A076746 A243706 A214696
KEYWORD
nonn,fini,full,base,nice
AUTHOR
EXTENSIONS
Single-digit terms added by Eric W. Weisstein.
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 29 05:48 EDT 2024. Contains 371265 sequences. (Running on oeis4.)