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A050420
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Numbers for which in base 2 the least number of digits that can be removed to leave a palindrome (possibly beginning with 0) is 1.
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4
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2, 4, 6, 8, 10, 11, 13, 14, 16, 18, 19, 22, 23, 25, 29, 30, 32, 34, 35, 36, 37, 41, 42, 43, 46, 47, 49, 53, 54, 55, 59, 61, 62, 64, 66, 67, 69, 76, 77, 81, 82, 83, 89, 90, 91, 94, 95, 97, 101, 102, 103, 109, 111, 115, 123, 125, 126, 128, 130, 131, 133, 136
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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EXAMPLE
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(18 base 2) = 10010 -> 1001.
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MAPLE
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filter:= proc(n) local L, R, k, m;
L:= convert(n, base, 2);
R:= ListTools:-Reverse(L);
m:= nops(L);
if L = R then return false fi;
ormap(i -> subsop(i=NULL, L)=subsop(m+1-i=NULL, R), [$1..m]);
end proc:
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PROG
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(Python)
def ok(n):
b = bin(n)[2:]
if b == b[::-1]: return False
for skip in range(len(b)):
newb = b[:skip] + b[skip+1:]
if len(newb) > 0 and newb == newb[::-1]:
return True
return False
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CROSSREFS
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Supersequence of A050425 (beginning with 1).
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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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