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.

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A273045 Fibonacci numbers with digits in nondecreasing order.

Original entry on oeis.org

0, 1, 1, 2, 3, 5, 8, 13, 34, 55, 89, 144, 233, 377
Offset: 1

Views

Author

Omar E. Pol, May 13 2016

Keywords

Comments

Intersection of A000045 and A009994. - Felix Fröhlich, May 16 2016
Conjecture: The sequence is finite, with 377 being the last term. I have verified the conjecture up to A000045(10^5). - Felix Fröhlich, May 16 2016
Conjecture verified up to Fibonacci(10^8). - Charles R Greathouse IV, May 17 2016

Crossrefs

Cf. A000045, A009994, A272918, A273046.

Programs

  • Mathematica
    Select[Fibonacci@ Range[0, 10^4], Sort@ # == # &@ IntegerDigits@ # &] (* Michael De Vlieger, May 13 2016 *)
  • PARI
    is_a009994(n) = digits(n)==vecsort(digits(n))
for(n=0, 1e4, if(is_a009994(fibonacci(n)), print1(fibonacci(n), ", "))) \\ Felix Fröhlich, May 16 2016
  • PARI
    fibmod(n,m)=lift(((Mod([1,1;1,0],m))^n)[1,2])
isA009994(n)=my(d=digits(n)); vecsort(d)==d
B1=10^9;B2=10^57;
for(n=1,1e9, if(isA009994(fibmod(n,B1)) && isA009994(fibmod(n,B2)) && isA009994(F=fibonacci(n)), print1(F", "))) \\ Charles R Greathouse IV, May 17 2016

Extensions

Offset adjusted by Felix Fröhlich, May 16 2016

A273003 Arrange the base 10 digits of the n-th Fibonacci number in descending order.

Original entry on oeis.org

0, 1, 1, 2, 3, 5, 8, 31, 21, 43, 55, 98, 441, 332, 773, 610, 987, 9751, 8542, 8411, 7665, 96410, 77111, 87652, 86643, 75520, 933211, 986411, 873111, 954221, 843200, 9664321, 9873210, 8755432, 8877520, 9765422, 95433210, 87754211, 99886310, 98665432
Offset: 0

Views

Author

Alonso del Arte, May 12 2016

Keywords

Comments

Conjecture: the largest Fibonacci number F(n) with its base 10 digits already sorted in descending order is F(16) = 987.

Examples

			a(7) = 31 because F(7) = 13, so the digits in descending order become 31.
a(8) = 21 = F(8), the digits are already in descending order.

Crossrefs

Cf. A000045, A004186, A272918, A273046.

Programs

  • Mathematica
    FromDigits[Reverse[Sort[IntegerDigits[#]]]]&/@Fibonacci[Range[0,50]] (* Harvey P. Dale, Sep 16 2016 *)
  • PARI
    a(n)=fromdigits(vecsort(digits(fibonacci(n)),,4)) \\ Charles R Greathouse IV, May 15 2016

Formula

a(n) = A004186(A000045(n)). - Michel Marcus, May 15 2016

Extensions

Corrected and extended by Harvey P. Dale, Sep 16 2016
Showing 1-2 of 2 results.

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

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