A008559 a(1)=2; thereafter, convert a(n-1) from base 10 to base 2 but regard the result as a base 10 number.

2, 10, 1010, 1111110010, 1000010001110100011000101111010

Offset

1,1

Comments

The previous number is converted to binary digits and then the digits are regarded as decimal digits in the next number in the sequence. - Michael Somos, May 16 2014

The next term has 100 digits. - Harvey P. Dale, Jul 16 2011

The number of decimal digits of a(n) is A242347(n). - Robert G. Wilson v, Jul 10 2013

Log(a(n)) / log(a(n-1)) = ~1/log_10(2) = A020862. - Robert G. Wilson v, Jul 10 2013

References

Clifford Pickover, Mazes for the Mind, St. Martin's Press, NY, 1992, p. 350.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..7

Maple

f:=proc(n) local i, j, r; i:=convert(n, base, 2); j:=add(i[r]*10^(r-1), r=1..nops(i)); end;
g:=proc(n, M) global f; local a, b, t1; a:=n; t1:=[a]; for i from 1 to M do b:=f(a); t1:=[op(t1), b]; a:=b; od; t1; end; g(2, 5); # N. J. A. Sloane, Jul 14 2015

Mathematica

NestList[FromDigits[IntegerDigits[#, 2]]&, 2, 5] (* Harvey P. Dale, Jul 16 2011 *)

Prog

(Python)
A008559_list = [2]
for _ in range(5):
....A008559_list.append(int(bin(A008559_list[-1])[2:]))
# Chai Wah Wu, Dec 26 2014

Crossrefs

Cf. A006937 (essentially the same sequence).

For initial terms 2 through 12 see A008559, A006938, A260025, A260024, A260026, A260027, A260028, A260029, A008559 (again), A006938 (again), A260030 respectively.

Sequence in context: A255587 A137890 A074333 * A245728 A171485 A291882

Adjacent sequences: A008556 A008557 A008558 * A008560 A008561 A008562

Keyword

nonn,base,nice

Author

N. J. A. Sloane

Extensions

Comment corrected by Chai Wah Wu, Dec 26 2014

Status

approved