A194041 Lucky numbers which are also unhappy numbers.

3, 9, 15, 21, 25, 33, 37, 43, 51, 63, 67, 69, 73, 75, 87, 93, 99, 105, 111, 115, 127, 135, 141, 151, 159, 163, 169, 171, 189, 195, 201, 205, 211, 223, 231, 235, 237, 241, 259, 261, 267, 273, 283, 285, 289, 297, 303, 307, 321, 327, 339, 349, 357, 361, 385, 393

Offset: 1

Author

Jonathan Vos Post, Aug 12 2011

Keywords

• nonn
• easy

Comments

An unhappy number is a number that is not happy (A007770) i.e., a number n such that iterating this sum-of-squared-digits map starting with n never reaches the number 1. Many asymptotic properties of the prime numbers are shared by the lucky numbers.

Links

• Nathaniel Johnston, Table of n, a(n) for n = 1..1000
• Eric W. Weisstein, Unhappy Number
• Eric W. Weisstein, Lucky Number

Crossrefs

Cf. A000959, A007770, A031177.

Formula

A000959 INTERSECTION A031177. {k such that k is in A000959 and k is not in A007770}.