A067521 Numbers n such that the square root of n is an integer and a multiple of the sum of the digits of n.
1, 81, 100, 324, 400, 1296, 2025, 2401, 2704, 2916, 4225, 5184, 6400, 7744, 8100, 10000, 11664, 12544, 20736, 26244, 32400, 33124, 36100, 39204, 40000, 46656, 59049, 63504, 72900, 75625, 88209, 104329, 104976, 122500, 123201, 129600
Offset: 1
Examples
18^2=324, 18=2*(3+2+4), so 324 is in the sequence.
Links
- Mehrad Mahmoudian, Table of n, a(n) for n = 1..10000
- Mehrad Mahmoudian, R code to produce the sequence
Programs
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Maple
dig := X->convert((convert(X,base,10)),`+`); seq(`if`(isprime(i)=false,`if`(i mod dig(i^2)=0,i^2,NULL),NULL),i=1..1000);
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Mathematica
Select[Range[500]^2,Divisible[Sqrt[#],Total[IntegerDigits[#]]]&] (* Harvey P. Dale, Jul 15 2013 *)
Extensions
More terms from Sascha Kurz and Francois Jooste (phukraut(AT)hotmail.com), Mar 18 2002
Definition corrected by Harvey P. Dale, Jul 15 2013