A378541 Practical numbers whose sum of divisors is even.

6, 12, 20, 24, 28, 30, 40, 42, 48, 54, 56, 60, 66, 78, 80, 84, 88, 90, 96, 104, 108, 112, 120, 126, 132, 140, 150, 156, 160, 168, 176, 180, 192, 198, 204, 208, 210, 216, 220, 224, 228, 234, 240, 252, 260, 264, 270, 272, 276, 280, 294, 300, 304, 306, 308, 312, 320, 330, 336, 340, 342, 348, 352, 360, 364, 368, 378, 380

Offset: 1

Author

Antti Karttunen and David A. Corneth, Dec 02 2024

Keywords

• nonn

Comments

Practical numbers without any squares or twice squares.

Examples

			20 is in the sequence as it is practical (every number from 1 through sigma(20) = 42 can be written as the sum of some distinct divisors of 20) and sigma(20) = 42 is even.
21 is not in the sequence as it is not practical.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Intersection of A005153 and A028983.

Setwise difference A083207 \ A353061.

Cf. A378540 (characteristic function).

Programs

PARI

isA378541 = A378540;