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A276713
Numbers n such that n and n+3 have the same number of divisors (A000005).
2
2, 35, 55, 62, 74, 82, 91, 102, 115, 119, 122, 135, 142, 143, 155, 158, 172, 186, 202, 203, 206, 214, 215, 218, 242, 255, 259, 262, 282, 295, 298, 299, 302, 323, 326, 343, 351, 354, 355, 362, 391, 395, 399, 425, 426, 435, 451, 466, 478, 482, 492, 502, 511, 514
OFFSET
1,1
LINKS
EXAMPLE
35 is in sequence because tau(35) = tau(38) = 4.
MAPLE
with(numtheory): A276713:=n->`if`(tau(n) = tau(n+3), n, NULL): seq(A276713(n), n=1..10^3); # Wesley Ivan Hurt, May 02 2017
MATHEMATICA
SequencePosition[DivisorSigma[0, Range[600]], {x_, _, _, x_}][[All, 1]] (* Harvey P. Dale, Nov 12 2022 *)
PROG
(Magma) [n: n in [1..10000] | NumberOfDivisors(n) eq NumberOfDivisors(n+3)]
(PARI) isok(n) = numdiv(n) == numdiv(n+3); \\ Michel Marcus, May 03 2017
CROSSREFS
Cf. A065559 (smallest k such that tau(k) = tau(k+n)), A015861 (sigma(n) = sigma(n+3)), A276714.
Cf. Similar sequences with numbers n such that n and n+k have the same number of divisors for k = 1: A005237, for k = 2: A062832.
Sequence in context: A041012 A291162 A042459 * A257601 A282727 A042353
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Sep 16 2016
STATUS
approved