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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A068520 Numbers n which can be transformed into a true arithmetic statement by inserting zero or more parentheses and elementary arithmetic operators ((, ), +, -, *, /) and one equality sign (=) as the rightmost insertion into the decimal representation of n. 0
11, 22, 33, 44, 55, 66, 77, 88, 99, 100, 101, 110, 111, 112, 122, 123, 133, 134, 144, 145, 155, 156, 166, 167, 177, 178, 188, 189, 199, 200, 202, 212, 213, 220, 221, 224, 235, 236, 246, 248, 257, 268, 279, 300, 303, 312, 313, 314, 321, 325, 326, 330, 331 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The minus sign is considered only as two-place infix operator, not as one-place prefix operator. Therefore -1 + 2 = 1 is not allowed and 121 is not a term.

For obvious reasons these numbers are called (elementary) "didactic numbers".

LINKS

Table of n, a(n) for n=1..53.

Index entries for similar sequences

EXAMPLE

7 = 7; 1 * 0 = 0; 2 - 2 = 0; 2 / 2 = 1; 18 / 2 = 9; 2 * (3 + 4) = 14. Therefore 77, 100, 220, 221, 1829 and 23414 are terms of the sequence.

CROSSREFS

Sequence in context: A087346 A060314 A109303 * A171901 A033283 A044851

Adjacent sequences:  A068517 A068518 A068519 * A068521 A068522 A068523

KEYWORD

base,nonn

AUTHOR

Joseph L. Pe, Mar 21 2002

EXTENSIONS

More terms from Larry Reeves (larryr(AT)acm.org), Jun 21 2002

Edited by Klaus Brockhaus, Jul 02 2003

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 October 14 04:29 EDT 2019. Contains 327995 sequences. (Running on oeis4.)