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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, Jan 11 2000 STATUS approved

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Last modified June 12 17:06 EDT 2024. Contains 373334 sequences. (Running on oeis4.)