A193996 Numbers that require exactly 8 iterations to determine that they are happy or not (A007770 and A031177).

4, 16, 20, 37, 42, 58, 89, 145, 78999, 79899, 79989, 79998, 87999, 89799, 89979, 89997, 97899, 97989, 97998, 98799, 98979, 98997, 99789, 99798, 99879, 99897, 99978, 99987, 378999, 379899, 379989, 379998, 387999, 389799, 389979, 389997, 389999, 397899, 397989

Offset: 1

Author

T. D. Noe, Aug 23 2011

Keywords

• nonn
• base

Comments

This sequence begins with the last 8 numbers of A039943. The number 78999 is the first happy number here.

Programs

Mathematica

f[n_] := Total[IntegerDigits[n]^2]; Select[Range[400000], Length[NestWhileList[f, #, UnsameQ, All]] - 1 == 8 &]