OFFSET
1,2
COMMENTS
All powers of 2 are in the sequence. - Chai Wah Wu, Nov 10 2014
Numbers k that divide A047778(k). - Michel Marcus, Nov 11 2014
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..145 (terms 1..54 from Chai Wah Wu)
EXAMPLE
3 is in the sequence because the concatenation is 1 10 11, binary expansion of 27, that is divisible by 3.
MATHEMATICA
Select[Range[2^13], Mod[FromDigits[Flatten[IntegerDigits[#, 2] & /@ Range@ #], 2], #] == 0 &] (* Michael De Vlieger, Aug 29 2015 *)
PROG
(PARI) lista(nn) = {vs = []; for (n=1, nn, vs = concat(vs, binary(n)); val = subst(Pol(vs), x, 2); if (val % n == 0, print1(n, ", ")); ); } \\ Michel Marcus, Nov 11 2014
(Python)
def ok(k): return concat_mod(2, k, k) == 0 # uses concat_mod by Jason Yuen in A029455
print([k for k in range(1, 10**5) if ok(k)]) # Michael S. Branicky, Apr 26 2026
CROSSREFS
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
More terms from Scott Lindhurst (ScottL(AT)alumni.princeton.edu)
More terms from David W. Wilson
a(47)-a(49) from Chai Wah Wu, Nov 10 2014
STATUS
approved
