

A053248


Second differences of sigma(n) that are negative.


2



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
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OFFSET

1,2


LINKS



FORMULA



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



KEYWORD

nonn


AUTHOR



STATUS

approved



