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A281004
Numbers with exactly 3 ones in both binary and ternary representations.
2
13, 37, 41, 49, 67, 97, 131, 133, 145, 193, 259, 265, 273, 289, 385, 517, 529, 577, 1027, 1029, 1033, 1041, 1153, 1281, 2053, 2057, 4101, 4105, 4113, 4129, 4161, 6145, 8195, 8197, 8209, 8225, 8257, 8321, 8449, 8705, 10241, 16449, 17409, 18433, 20481, 24577, 32771, 32777, 32785, 32801, 32833, 32897
OFFSET
1,1
COMMENTS
Intersection of A014311 and A023694.
All terms are odd, since n == A062756(n) (mod 2).
It is likely that a(136) = 1099528404993 is the last term. The next term, if any, is greater than 10^200.
LINKS
EXAMPLE
a(4) = 49 = 110001_2 = 1211_3.
MAPLE
R:= NULL: count:= 0:
for a from 2 while count < 136 do
for b from 1 to a-1 do
p:= 2^a + 2^b + 1;
if numboccur(1, convert(p, base, 3)) = 3 then
count:= count+1;
R:= R, p;
fi
od od:
R;
CROSSREFS
Cf. A014311, A023694, A062756. Contains A280997.
Sequence in context: A357444 A118361 A264908 * A088963 A301591 A301857
KEYWORD
nonn,base
AUTHOR
Robert Israel, Jan 12 2017
STATUS
approved