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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A215121 Strobogrammatic palindromic numbers in their Roman numeral representation. 0
1, 2, 3, 10, 19, 20, 30 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers which, written as Roman numerals, are the same upside down and backwards.

Upside-down-invariant numbers are also called ambigrams. "Upside down" here means rotated by 180° (i.e., central symmetry), NOT "vertically flipped" (symmetry w.r.t. horizontal line).

V, L, C, D, M (5, 50, 100, 500, 1000 in decimal) are not the same upside-down. Excludes "old style" Roman numeral representation of n (e.g. IIII rather than IV).

LINKS

Table of n, a(n) for n=1..7.

EXAMPLE

I, II, III, X, XIX, XX, XXX

CROSSREFS

Cf. A000787, A006968, A078715, A166874.

Sequence in context: A163467 A143045 A156909 * A175569 A275020 A122822

Adjacent sequences:  A215118 A215119 A215120 * A215122 A215123 A215124

KEYWORD

nonn,base,fini,full

AUTHOR

Jonathan Vos Post, Aug 03 2012

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 25 11:59 EDT 2019. Contains 324352 sequences. (Running on oeis4.)