A324174 Integers k such that 2*floor(sqrt(k)) divides k.

2, 4, 8, 12, 16, 24, 30, 36, 48, 56, 64, 80, 90, 100, 120, 132, 144, 168, 182, 196, 224, 240, 256, 288, 306, 324, 360, 380, 400, 440, 462, 484, 528, 552, 576, 624, 650, 676, 728, 756, 784, 840, 870, 900, 960, 992, 1024, 1088, 1122, 1156, 1224, 1260, 1296

Offset

1,1

Links

Table of n, a(n) for n=1..53.

Index entries for linear recurrences with constant coefficients, signature (1,0,2,-2,0,-1,1).

Formula

For k >= 1, a(3k-2) = 4k^2 - 2k, a(3k-1) = 4k^2 and a(3k) = 4k^2 + 4k.

Mathematica

Select[ Range[ 1000 ], Mod[ #, 2*Floor[ Sqrt[ # ]//N ] ]==0& ]
LinearRecurrence[{1, 0, 2, -2, 0, -1, 1}, {2, 4, 8, 12, 16, 24, 30}, 70] (* Harvey P. Dale, Dec 11 2022 *)

Prog

(PARI) is(n) = n%(2*sqrtint(n)) == 0;

Crossrefs

Cf. A006446, A324175, A324176, A324177, A324178.

Sequence in context: A260090 A351873 A256941 * A047836 A325762 A231958

Adjacent sequences: A324171 A324172 A324173 * A324175 A324176 A324177

Keyword

nonn

Author

Jinyuan Wang, Mar 09 2019

Status

approved