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 A225756 Runs of consecutive numbers with the same number of divisors. 3
 2, 3, 14, 15, 21, 22, 26, 27, 33, 34, 35, 38, 39, 44, 45, 57, 58, 75, 76, 85, 86, 87, 93, 94, 95, 98, 99, 104, 105, 116, 117, 118, 119, 122, 123, 133, 134, 135, 136, 141, 142, 143, 145, 146, 147, 148, 158, 159, 171, 172, 177, 178, 189, 190, 201, 202, 203 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The first run of length 3 is {33,34,35}; the first of length 4: {116, 117, 118, 119}; of length 5: {2641, 2642, 2643, 2644, 2645}; of length 6: {1081, 1082, 1083, 1084, 1085, 1086}; of length 7: {25781, 25782, 25783, 25784, 25785, 25786, 25787}; of length 8: {77673, 77674, 77675, 77676, 77677, 77678, 77679, 77680}. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 EXAMPLE Sequence begins: 2, 3; 14, 15; 21, 22; 26, 27; 33, 34, 35; 38, 39; etc. MATHEMATICA sel = Select[Range[300], DivisorSigma[0, #] == DivisorSigma[0, # + 1] &]; Union[sel, sel + 1] Flatten[SequencePosition[DivisorSigma[0, Range[300]], {x_, x_}]]//Union (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 22 2021 *) CROSSREFS Cf. A225757 (same sum of divisors). Cf. A225758 (same number and sum of divisors). Cf. A140578 (first term of every run). Sequence in context: A056435 A244295 A032806 * A260143 A275303 A281500 Adjacent sequences:  A225753 A225754 A225755 * A225757 A225758 A225759 KEYWORD nonn,easy,tabf AUTHOR Jean-François Alcover, May 15 2013 STATUS approved

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Last modified January 20 01:18 EST 2022. Contains 350467 sequences. (Running on oeis4.)