A050425 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 1.

2, 6, 10, 11, 13, 14, 18, 19, 23, 25, 29, 30, 34, 35, 37, 41, 42, 43, 47, 49, 53, 54, 55, 59, 61, 62, 66, 67, 69, 77, 81, 83, 89, 90, 91, 95, 97, 101, 102, 103, 109, 111, 115, 123, 125, 126, 130, 131, 133, 137, 145, 146, 147, 149, 157, 161, 163, 169, 170, 171

Offset

1,1

Links

Table of n, a(n) for n=1..60.

Example

(13 base 2) = 1101 -> 111.

Prog

(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[0] == '1' and newb == newb[::-1]:
            return True
    return False
print(list(filter(ok, range(172)))) # Michael S. Branicky, Aug 24 2021

Crossrefs

Subsequence of A050420 (possibly beginning with digit 0).

Cf. A050426, A050427, A050428, A050429.

Sequence in context: A337645 A225271 A357725 * A030405 A125241 A116043

Adjacent sequences: A050422 A050423 A050424 * A050426 A050427 A050428

Keyword

nonn,base

Author

Clark Kimberling

Status

approved