

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
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OFFSET

1,1


COMMENTS

The minus sign is considered only as twoplace infix operator, not as oneplace 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



