A219111 Numbers that eventually reach 1 under "x -> sum of 4th power of digits of x".

1, 10, 100, 1000, 10000, 11123, 11132, 11213, 11231, 11312, 11321, 12113, 12131, 12311, 13112, 13121, 13211, 21113, 21131, 21311, 23111, 31112, 31121, 31211, 32111, 44688, 44868, 44886, 46488, 46848, 46884, 48468, 48486, 48648, 48684, 48846, 48864, 64488

Offset: 1

Author

Michel Lagneau, Nov 12 2012

Keywords

• nonn
• base

Examples

			11123 is in the sequence because 1^4 +1^4+1^4+2^4+3^4 = 100 and 1^4 + 0^4 + 0^4 = 1.
2 is not in the sequence because  2 --> 16 --> 1297 -->8979 -->19619 -->14420 -->529 -->7202 -->2433 -->434 -->593 -->7267 -->6114 -->1554 -->1507 -->3027 -->2498 -->10929 -->13139 -->6725 -->4338 -->4514 -->1138 -->4179 -->9219 -->13139 which repeats with period 7, so never reaches 1.
		

Crossrefs

Cf. A007770, A035504.

Programs

Mathematica

Select[Range[50000], FixedPoint[Total[IntegerDigits[#]^4]&, #, 10]==1&]