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A060792 Numbers that are palindromic in bases 2 and 3. 29
0, 1, 6643, 1422773, 5415589, 90396755477, 381920985378904469, 1922624336133018996235, 2004595370006815987563563, 8022581057533823761829436662099, 392629621582222667733213907054116073, 32456836304775204439912231201966254787, 428027336071597254024922793107218595973 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Next term (if it exists) is greater than 3^66. - Keith F. Lynch, Jan 13 2014

a(17) (if it exists) is greater than 3^85. - Japheth Lim, Jan 14 2015

a(18) (if it exists) is greater than 3^93. - Ilya Nikulshin, Feb 22 2016

LINKS

Ilya Nikulshin, Table of n, a(n) for n = 1..17, extending earlier b-file from Japheth Lim.

Attila Bérczes and Volker Ziegler, On Simultaneous Palindromes, arXiv:1403.0787 [math.NT], 2014.

Alan Grimes, Keith F. Lynch, et al., Palindrome numbers

Keith F. Lynch, How I found big dual palindromes

EXAMPLE

6643 is a term: since 6643 = 1100111110011_2 = 100010001_3.

1422773 is a term: 1422773 = 101011011010110110101_2 = 2200021200022_3. - Vladimir Joseph Stephan Orlovsky, Sep 19 2009

MATHEMATICA

pal2Q[n_Integer] := IntegerDigits[n, 2] == Reverse[IntegerDigits[n, 2]]; pal3Q[n_Integer] := IntegerDigits[n, 3] == Reverse[IntegerDigits[n, 3]]; A060792 = {}; Do[If[pal2Q[n] && pal3Q[n], AppendTo[A060792, n]], {n, 12!}]; A060792 (* Vladimir Joseph Stephan Orlovsky, Sep 19 2009 *)

b1=2; b2=3; lst={}; Do[d1=IntegerDigits[n, b1]; d2=IntegerDigits[n, b2]; If[d1==Reverse[d1]&&d2==Reverse[d2], AppendTo[lst, n]], {n, 0, 2 10^7}]; lst (* Vincenzo Librandi, Feb 24 2016 *)

PROG

(PARI) ispal(n, b)=my(d=digits(n, b)); d==Vecrev(d)

is(n)=ispal(n, 2)&&ispal(n, 3) \\ Charles R Greathouse IV, Jun 17 2014

(Python)

from itertools import chain

from gmpy2 import digits, mpz

A060792 = [int(n, 2) for n in chain(map(lambda x:bin(x)[2:]+bin(x)[2:][::-1], xrange(1, 2**16)), map(lambda x:bin(x)[2:]+bin(x)[2:][-2::-1], xrange(1, 2**16))) if mpz(int(n, 2)).digits(3) == mpz(int(n, 2)).digits(3)[::-1]] # Chai Wah Wu, Aug 12 2014

(MAGMA) [n: n in [0..2*10^7] | Intseq(n, 3) eq Reverse(Intseq(n, 3))and Intseq(n, 2) eq Reverse(Intseq(n, 2))]; // Vincenzo Librandi, Feb 24 2016

CROSSREFS

A060792(3) = A048268(2) = A056749(3).

Sequence in context: A196510 A048268 A043634 * A119519 A233661 A131645

Adjacent sequences:  A060789 A060790 A060791 * A060793 A060794 A060795

KEYWORD

nonn,base,hard,more,nice

AUTHOR

Ulrich Schimke (ulrschimke(AT)aol.com)

EXTENSIONS

a(7) found by François Boisson, using a Caml program running on an AMD-64 machine. - Bruno Petazzoni, program co-author, Jan 31 2006

a(8) from the same source, May 26 2006

a(9) from Alan Grimes, Dec 16 2013

a(10) from Keith F. Lynch, Jan 07 2014

Term 0 prepended by Robert G. Wilson v, Oct 08 2014

a(11)-a(15) (from Alan Grimes and Keith F. Lynch) added by Japheth Lim, Jan 30 2014

a(16) from Japheth Lim, Jan 14 2015

a(17) from Ilya Nikulshin, using Core i7-3770@3.4GHz, 16GB RAM, Feb 22 2016

STATUS

approved

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Last modified March 26 23:14 EDT 2017. Contains 284138 sequences.