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A083794
Numbers n such that tau(n) is different from tau(n-1), where tau(m) = number of divisors of m.
2
1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 36, 37, 38, 40, 41, 42, 43, 44, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 77, 78, 79, 80, 81, 82
OFFSET
1,2
LINKS
P. Erdős, On a problem of Chowla and some related problems, Proc. Cambridge Philos. Soc. 32 (1936), pp. 530-540.
FORMULA
Erdős proved that a(n) ~ n. - Charles R Greathouse IV, Dec 05 2012
MAPLE
with(numtheory): for n from 1 to 150 do if tau(n) <> tau(n-1) then printf(`%d, `, n) fi: od: # James A. Sellers, May 19 2003
MATHEMATICA
a083794[n_] :=
Prepend[Select[Range[1, n],
DivisorSigma[0, #] != DivisorSigma[0, # - 1] &], 1]; a083794[82] (* Michael De Vlieger, Dec 24 2014 *)
PROG
(PARI) is(n)=numdiv(n-1)!=numdiv(n)
CROSSREFS
Cf. A083795.
Sequence in context: A326178 A162880 A083792 * A133016 A026503 A235498
KEYWORD
nonn
AUTHOR
Amarnath Murthy, May 07 2003
EXTENSIONS
More terms from James A. Sellers, May 19 2003
STATUS
approved