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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A109139 Numerators associated with the continued fraction of the differences of consecutive prime numbers.

Original entry on oeis.org

1, 2, 5, 12, 53, 118, 525, 1168, 5197, 32350, 69897, 451732, 1876825, 4205382, 18698353, 116395500, 717071353, 1550538206, 10020300589, 41631740562, 93283781713, 601334430840, 2498621505073, 15593063461278, 127243129195297
Offset: 0

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Author

Giorgio Balzarotti, Aug 18 2005

Keywords

Comments

The value of the continued fraction up to n is: R(n) = A(n)/B(n) where B(0) = 1, B(1) = a(1) *B(0), B(n) = a(n)* B(n - 1) + B(n-2) (n>=2).
From theory related to the continued fractions, we have:
- the continued fraction is a simple continued fraction (i.e., generated by integer positive numbers);
- the limit C0 (for n to infinity) exists, it is greater than 1 and is R(n) = A(n)/B(n) = C0 = 1.71010202343009...;
- the limit C0 is an irrational number;
- there is a unique simple continued fraction with limit C0;
- the generating number sequences of the simple continued fraction with limit C0 is unique;
- the sequence of generating numbers of the continued fraction (i.e., the difference of consecutive prime numbers and, consequently, the prime numbers) can be evaluated from C0 by:
a(0) = floor(C0), C1 = 1/(C0-a(0)), a(1) = floor(C1), C2 = 1/(C1-a(1)), ... a(n) = floor(Cn) ...;
- C0 satisfies the inequality: A(n)/B(n) - 1/B(n)^2 < C0 < A(n)/B(n) + 1/B(n)^2;
- this inequality allows us to evaluate the range of a(n+1), given A(n) and B(n);
- knowledge of A(n)/B(n) allows us to evaluate a(0), a(1) ..., a(n), i.e., the difference of consecutive prime numbers and, consequently, the prime numbers.
- The continued fraction derived from the sequences of consecutive prime number differences performs lower gradient w.r.t. the continued fraction based on prime sequence and it is therefore computationally easier to use.
The denominators B(n) are in A109140. Related sequences are D(n) = A(n) - B(n), S(n) = A(n) + B(n).

Examples

			n = 2, A(n) = A(2) = 5 because A(0) = 2-1 = 1, A(1) = (3-2) * A(0) + 1 = 2, A(2) = (5-3) * A(1) + 1 * A(0) = 5.
		

Crossrefs

Formula

A(0) = a(0), A(1) = a(1)*A(0) + 1, A(n) = a(n)*A(n - 1) + A(n-2) (n>=2) where a(0) = p(0) - 1, a(1) = p(1) - p(0), a(2) = p(2) - p(1) ..., a(n) = p(n) - p(n-1) where p(n) is the n-th prime number.

A110976 Sequence of numerators associated with the continued fraction based on the sequence d(n)= distance of n from closest prime ( A051699).

Original entry on oeis.org

2, 3, 2, 3, 5, 3, 8, 3, 11, 25, 36, 25, 61, 25, 86, 197, 283, 197, 480, 197, 677, 1551, 2228, 1551, 3779, 9109, 31106, 71321, 102427, 71321, 173748, 71321, 245069, 561459, 1929446, 4420351, 6349797, 4420351, 10770148, 25960647, 36730795, 25960647
Offset: 0

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Author

Keywords

Comments

The value of the continued fraction (for n to infinity) is 2.77459638163600405370875399896...; A(n) = A(n+2) if d(n) =2 and d(n+2) = 0

Examples

			if n = 2, A(n) = A(2) = 3 because A(0) = 2, A(1) = 1 * A(0) + 1 = 3, as the distances of n from closest prime are 2, 1, 0, 0, 1 ...
		

References

  • G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008, p. 110.

Crossrefs

Programs

  • Maple
    A[0]:=d[0]; A[1]:=d[1]*A[0]+1; B[0]:=1; B[1]:=d[1]*B[0]; for n from 2 by 1 to N do A[n]:=d[n]*A[n-1]+A[n-2]; B[n]:=d[n]*B[n-1]+B[n-2]; od;

Formula

See program

A110977 Sequence of denominators associated with the continued fraction based on the sequence d(n)= distance of n from closest prime ( A051699).

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 3, 1, 4, 9, 13, 9, 22, 9, 31, 71, 102, 71, 173, 71, 244, 559, 803, 559, 1362, 3283, 11211, 25705, 36916, 25705, 62621, 25705, 88326, 202357, 695397, 1593151, 2288548, 1593151, 3881699, 9356549, 13238248, 9356549, 22594797, 9356549
Offset: 0

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Author

Keywords

Examples

			if n = 2, B(n) = B(2) = 1 because B(0) = 1, B(1) = 1 * B(0) = 1 as the distances of n from closest prime are 2, 1, 0, 0, 1 ...
		

References

  • G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008, p. 110.

Crossrefs

Programs

  • Maple
    A[0]:=d[0]; A[1]:=d[1]*A[0]+1; B[0]:=1; B[1]:=d[1]*B[0]; for n from 2 by 1 to N do A[n]:=d[n]*A[n-1]+A[n-2]; B[n]:=d[n]*B[n-1]+B[n-2]; od;

Formula

See program.
Showing 1-3 of 3 results.