Let's be silly!

Logic Level 3

What's the next number in this sequence?

0 , 1 , 8 , 11 , 69 , 88 , . . . 0, 1, 8, 11, 69, 88,...


The answer is 96.

Otto Bretscher by Otto Bretscher , 65, USA

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

8 solutions

Pi Han Goh
May 6, 2015

All the numbers that are same when you look upside down!

89 NOPE, 90 NOPE, 91 NOPE, 92 NOPE, 93 NOPE, 94 NOPE, 95 NOPE, 96 YES!

38 Helpful 0 Interesting 0 Brilliant 0 Confused

Very nice! We can't always be so serious with our roots of unity and all ;)

Believe it or not , these guys actually have a name: Strobogrammatic numbers, with a rotational symmetry through 18 0 o 180^o , in some specified font.

Follow-up question: What about these: 11, 101, 181, 619, 16091,...

Otto Bretscher - 6 years, 1 month ago

Log in to reply

The follow-up sequence is that of the Strobogrammatic primes , the next in the sequence being 18181. 18181. Not surprisingly, there is no closed-form formula for these numbers. :)

P.S.. Here is the OEIS entry for the Strobogrammatic numbers.

Brian Charlesworth - 6 years, 1 month ago

Log in to reply

interesting....do they know whether there are infinitely many such primes?

Otto Bretscher - 6 years, 1 month ago

You need to try harder than that! It's the same as the previous sequence of numbers, but instead they are all prime numbers!

Pi Han Goh - 6 years, 1 month ago

Log in to reply

16191 NOPE, 16891, NOPE, 18081 NOPE, 18181 YES, BINGO!

Pi Han Goh - 6 years, 1 month ago

It was not meant to be hard ;)

Otto Bretscher - 6 years, 1 month ago

Log in to reply

@Otto Bretscher – Lemme post my sequence of problems in a moment

Pi Han Goh - 6 years, 1 month ago

@Otto Bretscher – CLICK HERE .

Pi Han Goh - 6 years, 1 month ago

Great observation!!

Aran Pasupathy - 6 years, 1 month ago

Thats what I did :) !

And Wa - 5 years, 9 months ago
Rama Devi
May 27, 2015

the following sequence are the elements of strobogrammatic number series.Therefore the next number is 96.

2 Helpful 0 Interesting 0 Brilliant 0 Confused
Irisae Jade
May 7, 2015

They are strobogrammatic numbers

1 Helpful 0 Interesting 0 Brilliant 0 Confused
Malik Muzammil
May 25, 2015

just taking the common .

0 Helpful 0 Interesting 0 Brilliant 0 Confused

96, the figures are the same if you turn them upside down.

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Zed Matubis
May 8, 2015

Ambigram in ascending order. 96

0 Helpful 0 Interesting 0 Brilliant 0 Confused

They are strobogrammatic numbers but one thing I don't understand why 6 is missing there ?

0 Helpful 0 Interesting 0 Brilliant 0 Confused

The symmetry is with respect to a rotation through 18 0 o 180^o ... the number 6 turns into a 9 this way.

Otto Bretscher - 6 years, 1 month ago

Log in to reply

okay now I got it . Thanks :)

অর্বি অর্বি - 6 years, 1 month ago
Dilip Mindfreak
May 8, 2015

I initially thought, why not '55' ??

0 Helpful 0 Interesting 0 Brilliant 0 Confused

5 and ϛ don't look the same.

Pi Han Goh - 6 years, 1 month ago

Log in to reply

Try using a really crummy calculator, and then 1, 2, 5 and 8 all turn upside down quite happily.

Joel Toms - 5 years, 10 months ago

The same case goes for 1 and 11 too...

Dilip Mindfreak - 6 years, 1 month ago

Log in to reply

In a certain font, 1 is an ambigram while 5 is not an ambigram.

It's clearly mentioned that 5 is not in the sequence, so we can conclude that 5 is not an ambigram for a certain font.

Pi Han Goh - 6 years, 1 month ago

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...