A249899 Numbers k such that sigma(k) contains the same digits as k in base 10.
1, 69, 211, 258, 270, 276, 433, 609, 639, 787, 877, 1021, 1201, 1231, 1255, 1291, 1321, 1433, 1621, 1721, 1787, 1877, 2011, 2111, 2131, 2141, 2161, 2204, 2311, 2391, 2411, 2556, 2676, 2711, 2931, 3121, 3343, 3409, 3413, 3433, 3463, 3554, 3643, 3678, 3679, 3877
Offset: 1
Examples
211 is in the sequence because the set of digits of n {1, 2} equals the set of digits of sigma(211) = 212.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Magma
[n: n in [1..10^5] | Set(Intseq(n)) eq Set(Intseq(SumOfDivisors(n)))];
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Mathematica
Select[Range[4000],Union[IntegerDigits[DivisorSigma[1,#]]] == Union[ IntegerDigits[#]]&] (* Harvey P. Dale, Dec 29 2015 *)
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PARI
isok(n) = Set(digits(n)) == Set(digits(sigma(n))); \\ Michel Marcus, May 27 2018
Comments