OFFSET
0,2
COMMENTS
In short, double the previous term and delete any digits appearing more than once.
Periodic with period 28.
Using the variant A320486 yields the same sequence, since the empty string never occurs. - M. F. Hasler, Oct 24 2018
Conjecture: If we start with any nonnegative integer and repeatedly double and apply the "delete multiple digits" map m -> A320485(m), we eventually reach 0 or 1 (see A323835). - N. J. A. Sloane, Feb 03 2019
REFERENCES
Eric Angelini, Posting to Sequence Fans Mailing List, Oct 24 2018
LINKS
EXAMPLE
2*32768 = 65536 -> 3 since we delete the multiple digits 6 and 5.
2*61 = 122 -> 1 since we delete the multiple 2's.
MATHEMATICA
a[1] = 1; a[n_] := a[n] = FromDigits[First /@ Select[ Tally[IntegerDigits[2 a[n - 1]]], #[[2]] == 1 &]] /* Stan Wagon, Nov 17 2018_ */
PROG
(PARI) A=[2]; for(i=1, 99, A=concat(A, A320486(A[#A]*2))); A \\ M. F. Hasler, Oct 24 2018
CROSSREFS
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Oct 24 2018, following a suggestion from Eric Angelini.
STATUS
approved