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

1,2

Links

Table of n, a(n) for n=1..81.

Formula

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

Example

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

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 *)

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.

Sequence in context: A112529 A352876 A161892 * A055565 A196088 A066498

Adjacent sequences: A056525 A056526 A056527 * A056529 A056530 A056531

Keyword

base,easy,nonn

Author

Henry Bottomley, Jun 19 2000

Status

approved