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

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A156761 Tribonacci primes that are also primes when their digits are reversed. 0
3, 5, 17, 31, 1201, 128199521 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This is to A115347 as Fibonacci numbers A000045 are to A000213 tribonacci numbers. Except for palidromatic tribonacci numbers {3, 5, ...} these are tribonacci emirps, A000213 INTERSECTION A006567.

The next term, if it exists, is greater than A000213(10000). [From Dmitry Kamenetsky, Mar 03 2009]

LINKS

Table of n, a(n) for n=1..6.

FORMULA

{p such that p is in A000040 and p is in A000213 and R(p) = A004086(p) is in A000040} = {p such that p is in A056816 and R(p) = is in A000040}.

EXAMPLE

a(5) = 1201 because 1201 is prime, and is the 13th tribonacci number A000213(13), and R(1201) = A004086(1201) = 1021 is also prime. a(6) = 128199521 = the 10th tribonacci prime A056816(10), and its digital reverse 125991821 is also prime.

MATHEMATICA

Select[LinearRecurrence[{1, 1, 1}, {1, 1, 1}, 200], AllTrue[{#, IntegerReverse[ #]}, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 31 2019 *)

CROSSREFS

Cf. A000040, A000045, A000213, A004086, A006567, A056816, A115347.

Sequence in context: A103149 A007802 A056816 * A151261 A148504 A148505

Adjacent sequences: A156758 A156759 A156760 * A156762 A156763 A156764

KEYWORD

more,nonn,base

AUTHOR

Jonathan Vos Post, Feb 15 2009

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 December 6 10:23 EST 2022. Contains 358630 sequences. (Running on oeis4.)