1, 7, 10, 13, 19, 23, 28, 31, 32, 44, 49, 68, 70, 79, 82, 86, 91, 94, 97, 100, 103, 109, 129, 130, 133, 139, 167, 176, 188, 190, 192, 193, 203, 208, 219, 226, 230, 236, 239, 262, 263, 280, 291, 293, 301, 302, 310, 313, 319, 320, 326, 329, 331, 338

Take for example 13. It is a Happy number.

(a) If you insert 0 to 13, you get, 103, 130

both of them are happy numbers.

Take 23, you get 203 and 230 ---> both are happy numbers.

What if you insert 2 zeros, would you get happy numbers?

Would this method always work?

(b) Now, if you insert 1 to say 13, you get, 113 (not a happy number, but a sad number) and 131 (a sad number)

(c) If you insert 2, it doesn't work

(d) If you insert 3 to 19, you get, 139 and 193 (both are happy numbers)

Would that always work?

Try inserting 4, 5, 6, 7, 8, and 9

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