A342040 Binary palindromes of odd length.

1, 101, 111, 10001, 10101, 11011, 11111, 1000001, 1001001, 1010101, 1011101, 1100011, 1101011, 1110111, 1111111, 100000001, 100010001, 100101001, 100111001, 101000101, 101010101, 101101101, 101111101, 110000011, 110010011, 110101011

Offset: 1

Author

Seiichi Manyama, Feb 26 2021

Keywords

• nonn
• base
• easy

Comments

Subsequence of A057148.

Crossrefs

Cf. A006995, A007088, A048700, A057148, A070939, A305989, A342036.

Programs

Mathematica

a[1] = 1; a[n_] := FromDigits[Join[#, {Mod[n, 2]}, Reverse[#]] &@ IntegerDigits[Floor[n/2], 2]]; Array[a, 26] (* Amiram Eldar, Apr 28 2021 *)

Python

def A342040(n):
    s = bin(n)[2:]
    return int(s+s[-2::-1]) # Chai Wah Wu, Feb 26 2021

Formula

a(n) = A007088(A048700(n)).