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A166550 Numbers n with property that n^2 and n-th prime have the same sum of digits. 1


%S 4,8,11,22,34,59,61,85,179,229,260,266,352,385,391,403,418,440,491,

%T 565,595,619,724,770,832,844,961,965,980,1012,1039,1069,1075,1099,

%U 1108,1127,1139,1148,1211,1217,1390,1468,1585,1589,1649,1747,1780,1789,1795,1799

%N Numbers n with property that n^2 and n-th prime have the same sum of digits.

%C A007605(n)=A004159(n).

%H Harvey P. Dale, <a href="/A166550/b166550.txt">Table of n, a(n) for n = 1..1000</a>

%e 4^2=16, prime(4)=7, 1+6=7

%e 8^2=64, prime(8)=19, 6+4=1+9

%e 11^2=121, prime(11)=31, 1+2+1=3+1

%e 22^2=484, prime(22)=79, 4+8+4=7+9

%e 34^2=1156, prime(22)=139, 1+1+5+6=1+3+9.

%t Position[Table[Plus@@IntegerDigits[Prime[n]]-Plus@@IntegerDigits[n^2],{n,1,3000}],0]//Flatten

%t Select[Range[2000],Total[IntegerDigits[#^2]]==Total[IntegerDigits[ Prime[ #]]]&] (* _Harvey P. Dale_, May 22 2015 *)

%Y Cf. A117224 Numbers for which the square and the cube have the same digital sum, A007605 Sum of digits of n-th prime, A004159 Sum of digits of n^2.

%K base,nonn

%O 1,1

%A _Zak Seidov_, Oct 16 2009

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Last modified August 11 04:03 EDT 2020. Contains 336421 sequences. (Running on oeis4.)