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A054007 Numbers k such that k and k+1 have the same sum but an unequal number of divisors. 4
206, 957, 1364, 2974, 4364, 14841, 18873, 19358, 20145, 24957, 36566, 56564, 74918, 79826, 79833, 92685, 111506, 116937, 138237, 147454, 161001, 162602, 174717, 190773, 193893, 201597, 230390, 274533, 347738, 416577, 422073, 430137 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..8304 (terms below 10^13, calculated from the b-file at A002961)
FORMULA
Members of A002961 which are not members of A054004
EXAMPLE
The divisors of 206 are 1, 2, 103, 206, so tau(206) = 4 and sigma(206) = 312; the divisors of 207 are 1, 3, 9, 23, 69, 207, so tau(207) = 6 and sigma(207) = 312. Hence, the integer 206 belongs to this sequence. - Bernard Schott, Oct 18 2019
MATHEMATICA
Select[Range[100000], DivisorSigma[0, #] != DivisorSigma[0, # + 1] && DivisorSigma[1, #] == DivisorSigma[1, # + 1] &] (* Jayanta Basu, Mar 20 2013 *)
CROSSREFS
Sequence in context: A113934 A260101 A113490 * A285754 A201032 A133149
KEYWORD
nonn
AUTHOR
Asher Auel, Jan 12 2000
EXTENSIONS
More terms from Jud McCranie, Oct 15 2000
STATUS
approved

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Last modified June 16 16:46 EDT 2024. Contains 373432 sequences. (Running on oeis4.)