A069067 Numbers k such that k*tau(k) is a perfect square.

1, 2, 36, 100, 108, 128, 196, 225, 256, 288, 441, 450, 484, 600, 675, 676, 800, 864, 882, 1089, 1156, 1176, 1225, 1296, 1323, 1350, 1444, 1521, 1568, 1944, 2000, 2116, 2178, 2450, 2601, 2646, 2904, 3025, 3042, 3240, 3249, 3267, 3364, 3844, 3872, 4056

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harvey P. Dale)

Mathematica

Select[Range[4200], IntegerQ[Sqrt[# DivisorSigma[0, #]]]&] (* Harvey P. Dale, Apr 21 2019 *)

Prog

(PARI) isok(k) = issquare(k * numdiv(k)); \\ Amiram Eldar, Feb 01 2025

Crossrefs

Cf. A000005, A038040.

Sequence in context: A328963 A081310 A187298 * A278930 A258356 A145450

Adjacent sequences: A069064 A069065 A069066 * A069068 A069069 A069070

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 05 2002

Status

approved