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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

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Last modified June 4 08:18 EDT 2020. Contains 334825 sequences. (Running on oeis4.)