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

1,1

Links

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

Example

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

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 *)

Crossrefs

Cf. A111592.

Sequence in context: A044122 A044503 A344072 * A331774 A216267 A012483

Adjacent sequences: A109803 A109804 A109805 * A109807 A109808 A109809

Keyword

nonn

Author

Jason Earls, Aug 16 2005

Status

approved