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 A230653 Numbers n such that tau(n+1) - tau(n) = 3; where tau(n) = the number of divisors of n (A000005). 6
 49, 99, 1023, 1681, 1935, 2499, 8649, 9603, 20449, 21903, 23715, 29583, 30975, 38024, 43263, 58563, 60515, 71824, 74528, 110223, 130321, 136899, 145924, 150543, 154449, 165649, 181475, 216224, 224675, 233288, 243049, 256035, 258063, 265225, 294849, 300303 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers n such that A051950(n+1) = 3. Numbers n such that A049820(n) - A049820(n+1) = 2. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..90 (* All terms up to 5 million. *) EXAMPLE Number 99 is in sequence because tau(100) - tau(99) = 9 - 6 = 3 MATHEMATICA Select[ Range[ 50000], DivisorSigma[0, # ] + 3 == DivisorSigma[0, # + 1] &] Position[Differences[DivisorSigma[0, Range[300400]]], 3]//Flatten (* Harvey P. Dale, Jun 30 2022 *) PROG (PARI) isok(n) = numdiv(n+1) - numdiv(n) == 3; \\ Michel Marcus, Oct 27 2013 CROSSREFS Cf. A055927 (numbers n such that tau(n+1) - tau(n) = 1), A230115 (numbers n such that tau(n+1) - tau(n) = 2), A000005. Sequence in context: A235578 A161689 A354342 * A019547 A228878 A067673 Adjacent sequences: A230650 A230651 A230652 * A230654 A230655 A230656 KEYWORD nonn AUTHOR Jaroslav Krizek, Oct 27 2013 EXTENSIONS More terms from Michel Marcus, Oct 27 2013 STATUS approved

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Last modified February 2 19:34 EST 2023. Contains 360024 sequences. (Running on oeis4.)