A050422 - OEIS

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A050422

Numbers for which in base 2 the least number of digits that can be removed to leave a palindrome (possibly beginning with 0) is 3.

2

52, 56, 88, 104, 112, 114, 116, 120, 142, 143, 150, 151, 168, 176, 184, 196, 200, 208, 212, 216, 220, 224, 226, 228, 233, 234, 236, 241, 242, 244, 248, 268, 270, 271, 278, 279, 282, 283, 286, 287, 302, 303, 304, 332, 334, 335, 336, 344, 352, 356, 360, 376, 388

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

(88 base 2) = 1011000 -> 0000.

PROG

(Python)

from itertools import combinations

def ok(n):

b = bin(n)[2:]

for digs_to_remove in range(4):

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

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

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

return (digs_to_remove == 3)

return False

print(list(filter(ok, range(390)))) # Michael S. Branicky, Aug 24 2021

CROSSREFS

Cf. A050427, A050420, A050421, A050423, A050424.

Sequence in context: A295156 A181461 A346455 * A350232 A226753 A260992

Adjacent sequences: A050419 A050420 A050421 * A050423 A050424 A050425

KEYWORD

nonn,base

AUTHOR

Clark Kimberling

STATUS

approved