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Numbers n such that digit sum of n^2 is 2*(digit sum of n).
1

%I #9 May 28 2021 13:27:07

%S 0,2,11,20,27,36,54,72,74,81,92,101,108,110,128,135,144,153,162,171,

%T 191,200,209,218,225,227,252,254,261,270,317,326,344,353,360,371,387,

%U 405,416,425,504,506,515,540,605,641,684,711,720,722,731,740,767,774,801

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

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

%C a(n) == {0 or 2} (mod 9). - _Robert G. Wilson v_, May 27 2009

%H Zak Seidov, <a href="/A159879/b159879.txt">Table of n, a(n) for n=1..3001</a>

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

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

%K base,nonn

%O 1,2

%A _Zak Seidov_, Apr 25 2009

%E Indices in b-file corrected by _N. J. A. Sloane_, Aug 31 2009