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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069881 Numbers n such that n and 2n+1 are both palindromes. 1
1, 2, 3, 4, 5, 55, 151, 161, 171, 181, 191, 252, 262, 272, 282, 292, 353, 363, 373, 383, 393, 454, 464, 474, 484, 494, 555, 5555, 15051, 15151, 15251, 15351, 15451, 16061, 16161, 16261, 16361, 16461, 17071, 17171, 17271, 17371, 17471, 18081, 18181 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Note that any number with all digits = 5 (A002279) is part of this sequence. - Jim McCann (jmccann(AT)umich.edu), Jul 16 2002

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..15636 (all terms up to 10^12)

EXAMPLE

151 is a member as 2*151 + 1 = 303 is also a palindrome.

MATHEMATICA

isPalin[n_]:=(n==FromDigits[Reverse[IntegerDigits[n]]]); Do[m = 2 n + 1; If[isPalin[n]&&isPalin[m], Print[n]], {n, 1, 10^5}] (* Vincenzo Librandi, Jan 22 2018 *)

PROG

(Perl) $a = 1; while((@b = split("|", $a) and @c = split("|", 2*$a+1) and (join("", reverse(@b)) eq join("", @b) and join("", reverse(@c)) eq join("", @c) and eval("print \"\$a \"; return 0; "))) or ++$a) { }

(PARI) isok(n) = (d=digits(n)) && (Vecrev(d)==d) && (dd=digits(2*n+1)) && (Vecrev(dd)==dd); \\ Michel Marcus, Jan 22 2018

CROSSREFS

Subsequence of A002113.

Sequence in context: A024638 A037330 A062939 * A004856 A037327 A075832

Adjacent sequences:  A069878 A069879 A069880 * A069882 A069883 A069884

KEYWORD

nonn,base

AUTHOR

Amarnath Murthy, Apr 30 2002

EXTENSIONS

More terms from Jim McCann (jmccann(AT)umich.edu), Jul 16 2002

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 June 26 00:10 EDT 2019. Contains 324367 sequences. (Running on oeis4.)