A053248 Second differences of sigma(n) that are negative.

1, 4, 10, 9, 11, 30, 10, 20, 40, 32, 16, 65, 13, 42, 82, 46, 12, 96, 26, 82, 106, 46, 18, 143, 57, 70, 114, 88, 40, 214, 26, 66, 136, 88, 120, 244, 30, 60, 160, 171, 47, 256, 36, 150, 266, 96, 40, 286, 88, 176, 226, 124, 12, 24, 342, 170, 230, 222, 94, 34, 443, 71

Offset

1,2

Links

Table of n, a(n) for n=1..62.

Formula

a(n) = A053223(A053229(n)).

Maple

with (numtheory): f := [seq( sigma(i+2) - sigma(i+1) - (sigma(i+1) - sigma(i)), i=1..200)];
seq(`if`(f[i] < 0, f[i], print( )), i=1..200);

Mathematica

Abs[Select[Differences[DivisorSigma[1, Range[200]], 2], Negative]] (* Harvey P. Dale, Aug 13 2015 *)

Crossrefs

Cf. A000203, A053223, A053247.

Sequence in context: A073722 A320577 A199805 * A081547 A264272 A264257

Adjacent sequences: A053245 A053246 A053247 * A053249 A053250 A053251

Keyword

nonn

Author

Asher Auel, Jan 11 2000

Status

approved