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A053247 Second differences of sigma(n) that are positive. 3
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 (list; graph; refs; listen; history; text; internal format)
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 (asher.auel(AT)reed.edu), Jan 11 2000

STATUS

approved

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Last modified August 5 00:15 EDT 2021. Contains 346456 sequences. (Running on oeis4.)