A109806 Admirable numbers such that the subtracted divisor is square.

20, 56, 104, 368, 464, 650, 836, 992, 1952, 8415, 11096, 16256, 17816, 28544, 31815, 45356, 77744, 83312, 91388, 98048, 113072, 122624, 128768, 130304, 254012, 351351, 388076, 507392, 522752, 537248, 698528, 780975, 791264, 1081568

Offset: 1

Author

Jason Earls, Aug 16 2005

Keywords

• nonn

Examples

			a(2)=56 because 1+2+7+8+14+28-4 = 56 and the subtracted divisor is square.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A111592.

Programs

Mathematica

aQ[n_] := (d = DivisorSigma[1, n] - 2n) > 0 && EvenQ[d] && Mod[n, d/2] == 0 && d < 2n && IntegerQ @ Sqrt[d/2]; Select[Range[10^5], aQ] (* Amiram Eldar, Sep 22 2019 *)