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A175242 a(n) = the number of divisors of n that are palindromes when written in binary. 2
1, 1, 2, 1, 2, 2, 2, 1, 3, 2, 1, 2, 1, 2, 4, 1, 2, 3, 1, 2, 4, 1, 1, 2, 2, 1, 4, 2, 1, 4, 2, 1, 3, 2, 3, 3, 1, 1, 2, 2, 1, 4, 1, 1, 6, 1, 1, 2, 2, 2, 4, 1, 1, 4, 2, 2, 2, 1, 1, 4, 1, 2, 6, 1, 3, 3, 1, 2, 2, 3, 1, 3, 2, 1, 4, 1, 2, 2, 1, 2, 4, 1, 1, 4, 4, 1, 2, 1, 1, 6, 2, 1, 4, 1, 2, 2, 1, 2, 5, 2, 1, 4, 1, 1, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

a(3) = 2 since 3 has 2 divisors, 1 and 3, that are palindromes when written in binary: 1 and 11.

MATHEMATICA

palbQ[n_]:=Module[{idn2=IntegerDigits[n, 2]}, idn2==Reverse[idn2]]; Table[ Count[ Divisors[ n], _?(palbQ[#]&)], {n, 110}] (* Harvey P. Dale, Mar 27 2019 *)

a[n_] := DivisorSum[n, 1 &, PalindromeQ @ IntegerDigits[#, 2] &]; Array[a, 100] (* Amiram Eldar, Jan 01 2020 *)

CROSSREFS

Cf. A006995.

Sequence in context: A035228 A035164 A023588 * A225843 A327657 A301957

Adjacent sequences:  A175239 A175240 A175241 * A175243 A175244 A175245

KEYWORD

base,nonn

AUTHOR

Leroy Quet, Mar 11 2010

EXTENSIONS

Extended by Ray Chandler, Mar 13 2010

STATUS

approved

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Last modified September 17 16:50 EDT 2021. Contains 347487 sequences. (Running on oeis4.)