cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-8 of 8 results.

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

Original entry on oeis.org

2, 10, 1010, 1111110010, 1000010001110100011000101111010
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

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)) ~ log_2(10) = A020862. - Robert G. Wilson v, Jul 10 2013

References

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

Links

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.

Programs

  • 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 *)
  • PARI
    lista(nn) = my(k=2); print1(k); for(n=2, nn, print1(", ", k=fromdigits(binary(k)))); \\ Jinyuan Wang, Jan 18 2025
  • Python
    A008559_list = [2]
for _ in range(5):
    A008559_list.append(int(bin(A008559_list[-1])[2:]))
# Chai Wah Wu, Dec 26 2014

Extensions

Comment corrected by Chai Wah Wu, Dec 26 2014

A006938 Convert the last term from decimal to binary! a(1)=3.

Original entry on oeis.org

3, 11, 1011, 1111110011, 1000010001110100011000101111011
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

Comments

The next term (a(6)) has 100 digits. - Harvey P. Dale, Feb 28 2012
The number of digits of a(n) are 1, 2, 4, 10, 31, 100, 330, 1093, 3628, 12049, 40023, 132951, 441651, 1467130, 4873698, 16190071, 53782249, 178660761, ... - Robert G. Wilson v, Jul 10 2013
log(a(n))/log(a(n-1)) ~ log_2(10) = A020862. - Robert G. Wilson v, Jul 10 2013

References

  • C. Pickover, Mazes for the Mind, St. Martin's Press, NY, 1992, p. 350.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

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

Programs

  • Mathematica
    NestList[FromDigits[IntegerDigits[#,2]]&,3,4] (* Harvey P. Dale, Feb 28 2012 *)
  • PARI
    lista(nn) = my(k=3); print1(k); for(n=2, nn, print1(", ", k=fromdigits(binary(k)))); \\ Jinyuan Wang, Jan 18 2025
  • Python
    def agen(an):
  while True: yield an; an = int(bin(an)[2:])
g = agen(3)
print([next(g) for i in range(5)]) # Michael S. Branicky, Mar 11 2021

Extensions

a(1)=3 added by N. J. A. Sloane, Jul 14 2015

A260024 Convert the last term from decimal to binary! a(1)=5.

Original entry on oeis.org

5, 101, 1100101, 100001100100101000101, 1010110101111001011010001101011011001100110110011001100101110100101
Offset: 1

Views

Author

N. J. A. Sloane, Jul 14 2015

Keywords

References

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

Crossrefs

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

Programs

  • Mathematica
    NestList[FromDigits[IntegerDigits[#,2]]&,5,5] (* Harvey P. Dale, Jun 23 2025 *)

A260025 Convert the last term from decimal to binary! a(1)=4.

Original entry on oeis.org

4, 100, 1100100, 100001100100101000100, 1010110101111001011010001101011011001100110110011001100101110100100
Offset: 1

Views

Author

N. J. A. Sloane, Jul 14 2015

Keywords

Crossrefs

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

Programs

  • Mathematica
    NestList[FromDigits[IntegerDigits[#,2]]&,4,5] (* Harvey P. Dale, Jun 11 2017 *)
  • PARI
    a(n) = my(k=4); for(i=2, n, k=fromdigits(binary(k))); k; \\ Jinyuan Wang, Jan 18 2025

A260026 Convert the last term from decimal to binary! a(1)=6.

Original entry on oeis.org

6, 110, 1101110, 100001100110100110110, 1010110101111001011010001101011100010111010110010110001101100011110
Offset: 1

Views

Author

N. J. A. Sloane, Jul 14 2015

Keywords

Crossrefs

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

Programs

  • PARI
    a(n) = my(k=6); for(i=2, n, k=fromdigits(binary(k))); k; \\ Jinyuan Wang, Jan 18 2025

A260028 Convert the last term from decimal to binary! a(1)=8.

Original entry on oeis.org

8, 1000, 1111101000, 1000010001110100000111001001000
Offset: 1

Views

Author

N. J. A. Sloane, Jul 14 2015

Keywords

Crossrefs

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

Programs

  • PARI
    a(n) = my(k=8); for(i=2, n, k=fromdigits(binary(k))); k; \\ Jinyuan Wang, Jan 18 2025

A260029 Convert the last term from decimal to binary! a(1)=9.

Original entry on oeis.org

9, 1001, 1111101001, 1000010001110100000111001001001
Offset: 1

Views

Author

N. J. A. Sloane, Jul 14 2015

Keywords

Crossrefs

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

A260030 Convert the last term from decimal to binary! a(1)=12.

Original entry on oeis.org

12, 1100, 10001001100, 1001010100000110110010101010001100
Offset: 1

Views

Author

N. J. A. Sloane, Jul 14 2015

Keywords

Comments

The next term has 110 digits. - Harvey P. Dale, May 15 2018

Crossrefs

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

Programs

  • Mathematica
    NestList[FromDigits[IntegerDigits[#,2]]&,12,4] (* Harvey P. Dale, May 15 2018 *)
Showing 1-8 of 8 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.