

A223078


Positive integers with the property that if the base4 representation is reversed the result is three times the original number.


2



75, 315, 1275, 5115, 19275, 20475, 76875, 81915, 307275, 322875, 327675, 1228875, 1290555, 1310715, 4915275, 4934475, 5161275, 5223675, 5242875, 19660875, 19741515, 20644155, 20890875, 20971515, 78643275, 78720075, 78969675, 82575675, 82652475, 83559675
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OFFSET

1,1


COMMENTS

From Robert Israel, Apr 23 2019: (Start)
All terms are divisible by 15.
If x is a term and x < 4^k, then x*(4^k+1) is a term. In particular the sequence is infinite. (End)


LINKS

Robert Israel, Table of n, a(n) for n = 1..985


MAPLE

rev4:= proc(n) local L, i;
L:= convert(n, base, 4);
add(L[i]*4^(i1), i=1..nops(L))
end proc:
Res:= NULL:
for d from 2 to 15 do
d1:= ceil(d/2); d2:= dd1;
for a from 4^(d11) to 4^d1/3 do
b:= rev4(a)/3 mod 4^d2;
x:= 4^d2*a+b;
if rev4(x) = 3*x then Res:= Res, x; fi
od od:
Res; # Robert Israel, Apr 23 2019


MATHEMATICA

Select[Range[84*10^6], 3#==FromDigits[Reverse[IntegerDigits[#, 4]], 4]&] (* Harvey P. Dale, Mar 03 2018 *)


CROSSREFS

Cf. A173951, A223077, A223079, A214927.
Sequence in context: A292313 A158765 A226741 * A055561 A193252 A223452
Adjacent sequences: A223075 A223076 A223077 * A223079 A223080 A223081


KEYWORD

nonn,base


AUTHOR

N. J. A. Sloane, Mar 14 2013


EXTENSIONS

More terms from Alois P. Heinz, Mar 14 2013


STATUS

approved



