login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A072016 Numbers k such that gcd(k, reverse(k)) = 27 = 3^3, where reverse(x) = A004086(x). 4

%I

%S 2889,3699,3888,3969,4779,4887,5589,5697,5778,5859,5886,5967,6399,

%T 6669,6777,6885,6939,7398,7479,7587,7668,7695,7749,7776,7857,7884,

%U 7938,7965,8289,8397,8559,8667,8775,8829,8883,8937,9099,9288,9369,9396,9477,9558,9585

%N Numbers k such that gcd(k, reverse(k)) = 27 = 3^3, where reverse(x) = A004086(x).

%C Solutions to gcd(k, reverse(k)) = 1,3,9 (lower powers of 3) are trivial (see A072005).

%H Vincenzo Librandi, <a href="/A072016/b072016.txt">Table of n, a(n) for n = 1..1030</a>

%e 2889 = 107*3*3*3, 9889 = 3*3*3*3*2*61.

%t Select[Range[10^4], GCD[#, FromDigits[Reverse[IntegerDigits[#]]]] == 27 &] (* _Vincenzo Librandi_, Jul 11 2018 *)

%o (PARI) isok(n) = gcd(n, fromdigits(Vecrev(digits(n)))) == 27; \\ _Michel Marcus_, Jul 11 2018

%o (MAGMA) [n: n in [1..10^4] | Gcd(n,Seqint(Reverse(Intseq(n)))) eq 27]; // _Vincenzo Librandi_, Jul 11 2018

%Y Cf. A004086, A055483, A069554, A071686, A072005.

%K nonn,base

%O 1,1

%A _Labos Elemer_, Jun 05 2002

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 18 18:17 EDT 2021. Contains 345120 sequences. (Running on oeis4.)