A159879 Numbers n such that digit sum of n^2 is 2*(digit sum of n).

0, 2, 11, 20, 27, 36, 54, 72, 74, 81, 92, 101, 108, 110, 128, 135, 144, 153, 162, 171, 191, 200, 209, 218, 225, 227, 252, 254, 261, 270, 317, 326, 344, 353, 360, 371, 387, 405, 416, 425, 504, 506, 515, 540, 605, 641, 684, 711, 720, 722, 731, 740, 767, 774, 801

Offset: 1

Author

Zak Seidov, Apr 25 2009

Keywords

• base
• nonn

Comments

A007953(n^2) = 2*A007953(n), sod(n^2) = 2*sod(n).

a(n) == {0 or 2} (mod 9). - Robert G. Wilson v, May 27 2009

Links

• Zak Seidov, Table of n, a(n) for n=1..3001

Crossrefs

A007953 Digital sum (i.e., sum of digits) of n. A004159 Sum of digits of n^2.

Programs

Mathematica

fQ[n_] := Plus @@ IntegerDigits[n^2] == 2 Plus @@ IntegerDigits@n; Select[ Range[0, 809], fQ@# &] (* Robert G. Wilson v, May 27 2009 *)

Extensions

Indices in b-file corrected by N. J. A. Sloane, Aug 31 2009