New in the #OEIS: the "it's my party and I'll cry if I want to" sequence: unhappy numbers sandwiched between two happy numbers.
https://oeis.org/A392990

A number is happy if the operation of squaring all its digits and summing the squares eventually leads to 1.

e.g.
68 → 100 → 1.
69 → 117 → 51 → 26 → 40 → 16 → 37 → 58 → 89 → 145 → 42 → 20 → 4 → 16 → ...
70 → 49 → 97 → 130 → 10 → 1

So 69 is in the sequence.