A177052 Ceiling(n/2)-abundant numbers.

6, 12, 18, 20, 24, 28, 30, 36, 40, 42, 48, 54, 56, 60, 66, 70, 72, 78, 80, 84, 88, 90, 96, 100, 102, 104, 108, 112, 114, 120, 126, 132, 138, 140, 144, 150, 156, 160, 162, 168, 174, 176, 180, 186, 192, 196, 198, 200, 204, 208, 210, 216, 220, 222, 224, 228

Offset: 1

Author

Vladimir Shevelev, Dec 09 2010

Keywords

• nonn

Comments

For definition, see A175522.

All positive numbers == 0 (mod 6) are in the sequence (basically A008588). In addition, note that all odd primes are ceiling(n/2)-deficient numbers. The first odd term of the sequence is 315.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A177050 (perfect version), A005100, A005101, A175524, A175526, A175811, A175821, A175853.

Programs

PARI

isok(n) = sumdiv(n, d, (d ceil(n/2); \\ Michel Marcus, Feb 08 2016

Sage

is_A177052 = lambda n: sum(ceil(d/2) for d in divisors(n)) > 2*ceil(n/2) # D. S. McNeil, Dec 10 2010

Formula

{n : Sum_{d|n, dA004526(1+d) > A004526(1+n)}. [R. J. Mathar, Dec 11 2010]