A176234 Floor(sqrt(n))-perfect numbers.

2, 3, 4, 21, 26, 27, 33, 35, 38, 46, 58, 62, 74, 475, 605, 1083, 1719, 2007, 2151, 2169, 2259, 2313, 2421, 2431, 2439, 2493, 2529, 2547, 2637, 2737, 2763, 2799, 2979, 3123, 3303, 3357, 3367, 3451, 3619, 3681, 3698, 4255, 4465, 4625, 5035, 5125, 5185, 5695, 6205

Offset: 1

Author

Vladimir Shevelev, Dec 07 2010

Keywords

• nonn

Comments

See definition in comment to A175522.

The even terms begin: 2, 4, 26, 38, 46, 58, 62, 74, 3698, 34226, 34726, ... - Michel Marcus, Feb 08 2016

Examples

			floor(sqrt(35))=5; floor(sqrt(1))+floor(sqrt(5))+floor(sqrt(7))=5. Therefore, 35 is in the sequence.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A175522, A000396, A175807.

Programs

Mathematica

f[n_] := Sum[Floor[Sqrt[Divisors[n][[i]]]], {i, 1, Length[Divisors[n]] - 1}]; Select[Range[3000], f[#] == Floor[Sqrt[#]] &]

PARI

isok(n) = sumdiv(n, d, (dMichel Marcus, Feb 08 2016

Extensions

More terms from Michel Marcus, Feb 08 2016