A153211 Sum of digits of n, times digital reversal of sum of digits of n.

1, 4, 9, 16, 25, 36, 49, 64, 81, 1, 4, 9, 16, 25, 36, 49, 64, 81, 10, 4, 9, 16, 25, 36, 49, 64, 81, 10, 121, 9, 16, 25, 36, 49, 64, 81, 10, 121, 252, 16, 25, 36, 49, 64, 81, 10, 121, 252, 403, 25, 36, 49, 64, 81, 10, 121, 252, 403, 574, 36, 49, 64, 81, 10, 121, 252, 403, 574

Offset

1,2

Comments

The fixed points of this sequence {n such that a(n) = n} are A110921.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = SOD(n)*R(SOD(n)) = A007953(n)*A004086(A007953(n)).

Example

a(19) = (1+9)*R(1+9) = 10*01 = 10*1 = 10. a(79) = 976 because (7+9)*R(7+9) = 16*61 = 976.

Mathematica

Table[With[{ds=Total[IntegerDigits[n]]}, IntegerReverse[ds]ds], {n, 70}] (* Harvey P. Dale, Mar 07 2023 *)

Crossrefs

Cf. A004086, A007953, A110921.

Sequence in context: A003132 A062331 A069940 * A118881 A370812 A277342

Adjacent sequences: A153208 A153209 A153210 * A153212 A153213 A153214

Keyword

base,easy,nonn

Author

Jonathan Vos Post, Dec 20 2008

Status

approved