The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A305409 Positive numbers that can be expressed as the product of 1 or more binary palindromes (elements of A006995). 1
 1, 3, 5, 7, 9, 15, 17, 21, 25, 27, 31, 33, 35, 45, 49, 51, 63, 65, 73, 75, 81, 85, 93, 99, 105, 107, 119, 125, 127, 129, 135, 147, 153, 155, 165, 175, 189, 195, 217, 219, 225, 231, 243, 245, 255, 257, 273, 279, 289, 297, 313, 315, 321, 325, 341, 343, 357, 365 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Robert Israel, Table of n, a(n) for n = 1..3086 EXAMPLE 155 is in the sequence because it is 5*31, and both 5 and 31 are palindromic numbers (with binary representations 101 and 11111, respectively). MAPLE dmax:= 10: N:= 2^dmax: # to get all terms < N revdigs:= proc(n)   local L, Ln, i;   L:= convert(n, base, 2);   Ln:= nops(L);   add(L[i]*2^(Ln-i), i=1..Ln); end proc: A:= {}: for d from 2 to dmax do if d::even then     A:= A union {seq(2^(d/2)*x + revdigs(x), x=2^(d/2-1)..2^(d/2)-1)} else     m:= (d-1)/2;     B:={seq(2^(m+1)*x + revdigs(x), x=2^(m-1)..2^m-1)};     A:= A union B union map(`+`, B, 2^m) fi od: R:= {1}: for b in A do   R:= map(t -> seq(t*b^j, j=0..floor(log[b](N/t))), R) od: sort(convert(R, list)); # Robert Israel, Jun 01 2018 CROSSREFS Cf. A006995. Sequence in context: A121820 A258159 A238257 * A329358 A180204 A006995 Adjacent sequences:  A305406 A305407 A305408 * A305410 A305411 A305412 KEYWORD nonn,base AUTHOR Jeffrey Shallit, May 31 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 24 12:13 EST 2020. Contains 332209 sequences. (Running on oeis4.)