A056528 Sum of digits of square of sum of digits of square.

1, 7, 9, 13, 13, 9, 16, 1, 9, 1, 7, 9, 13, 13, 9, 16, 10, 9, 1, 7, 9, 13, 13, 9, 16, 10, 9, 10, 16, 9, 13, 13, 9, 16, 1, 9, 10, 16, 9, 13, 13, 9, 16, 10, 9, 1, 16, 9, 13, 13, 9, 16, 10, 9, 1, 16, 9, 13, 13, 9, 16, 10, 18, 10, 16, 9, 13, 13, 9, 16, 1, 9, 10, 16, 9, 13, 13, 9, 16, 1, 9

Offset: 1

Author

Henry Bottomley, Jun 19 2000

Keywords

• base
• easy
• nonn

Examples

			a(2)=7 because sum of digits of square of 2 is 4 and sum of digits of square of 4 is 1+6=7
		

Crossrefs

Cf. A004159 for sum of digits of square, A056020 where iteration settles to 1, A056020 where iteration settles to 9, A056527 where iteration settles to 13 and 16. See also A056529.

Programs

Mathematica

Array[Total[IntegerDigits[(Total[IntegerDigits[#^2]])^2]]&,90] (* Harvey P. Dale, Jan 17 2012 *)
Table[Nest[Total[IntegerDigits[#^2]]&,n,2],{n,90}] (* Harvey P. Dale, Mar 07 2018 *)

Formula

a(n)=A004159(A004159(n))