A210888 Dates after Jan 01 00 in chronological order which are palindromic when they are written in the format DD.MM.YY. The terms are listed as numbers (without the dots). Leading zeros of the terms are suppressed.

101101, 201102, 301103, 11110, 111111, 211112, 21120, 121121, 221122, 31130, 131131, 231132, 41140, 141141, 241142, 51150, 151151, 251152, 61160, 161161, 261162, 71170, 171171, 271172, 81180, 181181, 281182, 91190, 191191, 291192

Offset

1,1

Comments

There are exactly 30 such palindromic dates between Jan 1 00 and Dec 31 99 (see b-file for the complete list).

See A210887 for the number of days after 'Mar 1 00' to get such a palindromic date.

Links

Hieronymus Fischer, Table of n, a(n) for n = 1..30

Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).

Formula

a(n) = DDMMYY_date('Mar 1 00' + A210887(n)).

From Chai Wah Wu, Feb 03 2021: (Start)

a(n) = a(n-1) + a(n-3) - a(n-4) for n > 7.

G.f.: x*(100001*x^6 - 391094*x^3 + 100001*x^2 + 100001*x + 101101)/(x^4 - x^3 - x + 1). (End)

a(n) ~ 10010*n/3. - Charles R Greathouse IV, May 28 2026

Example

The first palindromic date in DD.MM.YY format after 'Jan 01 00' is a(1)=101101 (='10.11.01' = 'Nov 10 01' = 'Mar 01 00' + A210887(1) days);
The sixth palindromic date in DD.MM.YY format after 'Jan 01 00' is a(6)=211112 (='21.11.12' = 'Nov 21 12' = 'Mar 01 00' + A210887(6) days).
The last (30th) palindromic date in DD.MM.YY format after 'Jan 01 00' is a(30)=291192 (='29.11.92' = 'Nov 29 92' = 'Mar 01 00' + A210887(30) days).

Prog

(PARI) a(n)=if(n>3, (10010*n+11*[52116, -610, 25753][n%3+1])/3, 100001*n+1100) \\ Charles R Greathouse IV, May 28 2026

Crossrefs

Cf. A210883-A210887, A210889-A210895, A106605, A107273, A107275

Sequence in context: A107274 A107276 A068445 * A115828 A168529 A255976

Adjacent sequences: A210885 A210886 A210887 * A210889 A210890 A210891

Keyword

nonn,base,easy,changed

Author

Hieronymus Fischer, Apr 01 2012

Status

approved