login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A090707 Primes whose decimal representation is a valid number in base 4 and interpreted as such is again a prime. 79
2, 3, 11, 13, 23, 31, 101, 103, 113, 131, 211, 223, 233, 311, 331, 1013, 1021, 1033, 1103, 1201, 1213, 1223, 1231, 1301, 2003, 2111, 2113, 2131, 2203, 2213, 2311, 2333, 3001, 3011, 3203, 3221, 3301, 3323, 10111, 10211, 10303, 10313, 10321, 10331 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

13 is prime in decimal and also when considered as a number in base 4: 13 [base 4] = 7 [base 10] which is also prime.

MATHEMATICA

Select[ FromDigits@# & /@ IntegerDigits[ Prime@ Range@ 270, 4], PrimeQ] (* Robert G. Wilson v, Jan 05 2014 *)

PROG

(PARI) forprime(p=2, 1e4, if(isprime(t=fromdigits(digits(p, 4))), print1(t", "))) \\ Charles R Greathouse IV, Apr 22 2015

CROSSREFS

Cf. A031974, A089971, A089981, A090708, A090709, A090710, A235394, A235395, A000040.

Sequence in context: A076503 A004678 A107715 * A062350 A163498 A038874

Adjacent sequences:  A090704 A090705 A090706 * A090708 A090709 A090710

KEYWORD

base,nonn

AUTHOR

Cino Hilliard, Jan 18 2004

EXTENSIONS

Name, example and offset corrected by M. F. Hasler, Jan 03 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 18 23:46 EST 2018. Contains 318245 sequences. (Running on oeis4.)