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A056528
Sum of digits of square of sum of digits of square.
2
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
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
KEYWORD
base,easy,nonn
AUTHOR
Henry Bottomley, Jun 19 2000
STATUS
approved