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A241491
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2*n is not the sum of two base-2 palindromes
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7
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88, 94, 104, 121, 122, 155, 262, 314, 328, 368, 377, 397, 416, 431, 433, 434, 440, 466, 472, 497, 500, 590, 620, 654, 655, 664, 671, 676, 688, 704, 710, 716, 720, 905, 945, 961, 973, 977, 1063, 1103, 1114, 1131, 1228, 1234, 1249, 1250, 1270, 1312, 1343, 1348
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OFFSET
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1,1
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COMMENTS
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Note that since all nonzero base-2 palindromes are odd, the sum of two nonzero base-2 palindromes is even.
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LINKS
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EXAMPLE
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86 is not in the sequence because 2*86 = 7 + 165, and 7 and 165 are in A006995.
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MAPLE
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N:= 15; # for all entries up to 2^(N-1)
with(SignalProcessing): # requires Maple 17+
rev2:= proc(n) option remember;
rev2(floor(n/2)) + (n mod 2)*2^ilog2(n)
end;
rev2(0) := 0; rev2(1):= 1;
B:= Array(1..2^N, datatype=float[8]);
for d from 1 to N do
d1:= ceil(d/2);
for x from 2^(d1-1) to 2^d1-1 do
if d::even then y:= x*2^d1+rev2(x)
else y:= x*2^(d1-1)+rev2(floor(x/2));
fi;
B[y]:= 1;
od od:
B2:= Convolution(B, B);
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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