A227983 Numbers n such that sigma(n+1) - sigma(n-1) < sigma(n); where sigma(n) = A000203(n) = sum of the divisors of n.

4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73

Offset

1,1

Comments

See A076530 - numbers n such that sigma(n+1) - sigma(n-1) = sigma(n).

Complement of union of A076530, A227982 and number 1.

Links

Jaroslav Krizek, Table of n, a(n) for n = 1..2000

Example

Number 60 is in the sequence because sigma(61) - sigma(59) = 62 - 60 = 2 < sigma(60) = 168.

Mathematica

Flatten[Position[Partition[DivisorSigma[1, Range[100]], 3, 1], _?(#[[3]]- #[[1]]< #[[2]]&), 1, Heads->False]]+1 (* Harvey P. Dale, Jul 25 2021 *)

Crossrefs

Cf. A076530, A000203, A227982.

Sequence in context: A171463 A020705 A081313 * A081333 A026419 A026434

Adjacent sequences: A227980 A227981 A227982 * A227984 A227985 A227986

Keyword

nonn

Author

Jaroslav Krizek, Aug 08 2013

Status

approved