A383638 Right-truncatable happy numbers: every prefix is a happy number and no digits are zero.

1, 7, 13, 19, 79, 133, 139, 192, 193, 793, 1332, 1333, 1335, 1337, 1339, 1393, 1929, 1933, 7937, 7938, 13323, 13332, 13334, 13339, 13393, 13933, 19293, 19295, 19296, 19333, 79372, 79384, 79386, 133236, 133326, 133399, 133939, 139339, 192934, 192951, 192954

Offset: 1

Author

Shyam Sunder Gupta, May 03 2025

Keywords

• nonn
• base
• fini
• full

Comments

Happy numbers in which repeatedly deleting the least significant digit gives a happy number at every step until a single-digit happy number remains. Last term is a(170) = 1933396239639.

Links

• Shyam Sunder Gupta, Table of n, a(n) for n = 1..170
• Shyam Sunder Gupta, Happy Numbers, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 7, 209-222.

Crossrefs

Cf. A007770.