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A050427 Numbers for which in base 2 the least number of digits that can be removed to leave a base 2 palindromic number (beginning with 1) is 3. 4

%I

%S 8,24,40,44,52,56,72,76,78,92,100,114,116,120,136,140,142,143,148,150,

%T 151,158,164,168,172,174,188,196,210,212,216,220,226,233,234,236,241,

%U 242,244,248,264,268,270,271,276,278,279,282,283,287,303,308,310,318

%N Numbers for which in base 2 the least number of digits that can be removed to leave a base 2 palindromic number (beginning with 1) is 3.

%e (72 base 2) = 1001000 -> 1001.

%o (Python)

%o from itertools import combinations

%o def ok(n):

%o b = bin(n)[2:]

%o for digs_to_remove in range(4):

%o for skip in combinations(range(len(b)), digs_to_remove):

%o newb = "".join(b[i] for i in range(len(b)) if i not in skip)

%o if len(newb) > 0 and newb[0] == '1' and newb == newb[::-1]:

%o return (digs_to_remove == 3)

%o return False

%o print(list(filter(ok, range(320)))) # _Michael S. Branicky_, Aug 24 2021

%Y Cf. A050425, A050426, A050428, A050429.

%K nonn,base

%O 1,1

%A _Clark Kimberling_

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Last modified October 19 10:57 EDT 2021. Contains 348076 sequences. (Running on oeis4.)