A053227 First differences of sigma(n) that are negative.

1, 4, 2, 6, 14, 13, 19, 10, 12, 29, 2, 26, 40, 15, 6, 53, 4, 48, 52, 6, 6, 24, 67, 21, 44, 48, 40, 30, 106, 43, 76, 30, 72, 121, 44, 88, 65, 42, 116, 12, 90, 122, 40, 24, 154, 15, 115, 112, 18, 30, 54, 170, 64, 134, 96, 28, 2, 36, 227, 18, 68, 184, 79, 120, 176, 132, 148

Offset: 1

Author

Asher Auel, Jan 06 2000

Keywords

• nonn

Links

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

Crossrefs

Cf. A000203, A053222, A053225.

Programs

Maple

with(numtheory): seq( `if`((sigma(i) > sigma(i+1)),(sigma(i) - sigma(i+1)),print( )), i=1..200);

Mathematica

Abs[Select[Differences[DivisorSigma[1,Range[200]]],#<0&]] (* Harvey P. Dale, Apr 17 2022 *)

Formula

a(n) = A053222(A053226(n))