A number is called
strobogrammatic if it remains the same when read
upside down. Usually strobogrammatic numbers are made only of digits
,
,
,
, and
.
However, since the diffusion of pocket calculators, also the digits 2 and 5 can be considered valid by some authors.
The first strobogrammatic numbers are
1, 8, 11, 69, 88, 96, 101, 111, 181, 609, 619, 689, 808, 818, 888, 906, 916, 986, 1001, 1111, 1691, 1881, 1961, 6009, 6119, 6699, 6889, 6969, 8008, 8118, 8698, 8888, 8968, 9006 more terms
Pictorial representation of remainders (mod 2, 3, ...,11) frequency. For a table of values and more details
click here
A graph displaying how many strobogrammatic numbers are multiples of the primes
p from 2 to 71. In black the ideal line 1/
p.