A053247 Second differences of sigma(n) that are positive.

2, 7, 11, 7, 22, 24, 7, 34, 41, 14, 48, 40, 18, 68, 71, 21, 49, 75, 38, 102, 92, 100, 103, 47, 110, 96, 50, 138, 140, 15, 103, 134, 78, 195, 161, 6, 116, 194, 70, 182, 140, 72, 234, 178, 56, 156, 227, 76, 229, 218, 226, 276, 160, 260, 162, 26, 252, 280, 74, 224

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = A053223(A053228(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

Select[Differences[DivisorSigma[1, Range[150]], 2], #>0&] (* Harvey P. Dale, May 10 2012 *)

Crossrefs

Cf. A000203, A053223, A053248.

Sequence in context: A241807 A020638 A091385 * A226089 A208846 A087723

Adjacent sequences: A053244 A053245 A053246 * A053248 A053249 A053250

Keyword

nonn

Author

Asher Auel, Jan 11 2000

Status

approved