A069881 Numbers n such that n and 2n+1 are both palindromes.

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

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 A325653 A037327

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