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

1,1

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

Formula

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

Prog

(Sage) is_A177052 = lambda n: sum(ceil(d/2) for d in divisors(n)) > 2*ceil(n/2) # D. S. McNeil, Dec 10 2010
(PARI) isok(n) = sumdiv(n, d, (d<n)*ceil(d/2)) > ceil(n/2); \\ Michel Marcus, Feb 08 2016

Crossrefs

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

Sequence in context: A097216 A346695 A326133 * A023196 A376880 A204829

Adjacent sequences: A177049 A177050 A177051 * A177053 A177054 A177055

Keyword

nonn

Author

Vladimir Shevelev, Dec 09 2010

Status

approved