What is the sequence of 3354435543?

Answer 1

At first glance, it seems that the sequence is: +2, -1, -1, and every other number is written twice.

However, these are the lengths of the words that represent digits 1 through 10 in English.

One - 3 letters

Two - 3 letters

Three - 5 letters

Four - 4 letters

Five - 4 letters

Six - 3 letters

Seven - 5 letters

Eight - 5 letters

Nine - 4 letters

Ten - 3 letters

So while the sequence at the top seems to hold, the problem is that it breaks after the first ten digits.

Eleven - 6 letters

Twelve - 6 letters

Thirteen - 8 letters

Fourteen - 8 letters

Fifteen - 7 letters

Sixteen - 7 letters

Seventeen - 9 letters

Eighteen - 8 letters