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 A335252 Numbers k such that k and k+2 have the same unitary abundance (A129468). 2
 12, 63, 117, 323, 442, 1073, 1323, 1517, 3869, 5427, 6497, 12317, 18419, 35657, 69647, 79919, 126869, 133787, 151979, 154007, 163332, 181427, 184619, 333797, 404471, 439097, 485237, 581129, 621497, 825497, 1410119, 2696807, 3077909, 3751619, 5145341, 6220607 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Are 12, 442 and 163332 the only even terms? Are there any unitary abundant numbers (A034683) in this sequence? No further even terms up to 10^13. - Giovanni Resta, May 30 2020 LINKS Amiram Eldar, Table of n, a(n) for n = 1..300 EXAMPLE 12 is a term since 12 and 14 have the same unitary abundance: A129468(12) = usigma(12) - 2*12 = 20 - 24 = -4, and A129468(14) = usigma(14) - 2*14 = 24 - 28 = -4. MATHEMATICA usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); udef[n_] := 2*n - usigma[n]; Select[Range[10^5], udef[#] == udef[# + 2] &] CROSSREFS The unitary version of A330901. Cf. A034448, A034683, A129468, A129487, A335251. Sequence in context: A196335 A349159 A092224 * A212509 A212249 A309372 Adjacent sequences: A335249 A335250 A335251 * A335253 A335254 A335255 KEYWORD nonn AUTHOR Amiram Eldar, May 28 2020 STATUS approved

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Last modified April 16 03:17 EDT 2024. Contains 371696 sequences. (Running on oeis4.)