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!)
A244085 Primes p such that the concatenation of p and 2*p-1 is also prime. 1
2, 5, 17, 29, 47, 61, 137, 149, 179, 181, 227, 251, 349, 367, 409, 457, 461, 479, 487, 557, 569, 617, 661, 691, 761, 787, 809, 821, 859, 911, 971, 977, 997, 1039, 1117, 1129, 1151, 1249, 1277, 1367, 1439, 1447, 1459, 1481, 1559, 1571, 1667, 1747, 1801, 1831 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The corresponding prime numbers are: (23, 59, 1733, 2957, 4793, 61121, ...).
LINKS
EXAMPLE
17 in this sequence because the concatenation of 17 and 33 is 1733 prime.
MATHEMATICA
p2pQ[n_]:=PrimeQ[FromDigits[IntegerDigits/@Join[n, 2 n - 1]]]; Select[Prime[Range[900]], p2pQ]
CROSSREFS
Cf. A168164.
Sequence in context: A195271 A077217 A120847 * A019353 A106882 A172122
KEYWORD
nonn,base
AUTHOR
Vincenzo Librandi, Jun 22 2014
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 February 27 14:08 EST 2024. Contains 370375 sequences. (Running on oeis4.)