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 1-4 of 4 results.

A376052 Lexicographically earliest sequence of positive integers a(1), a(2), a(3), ... such that for any n > 0, S(n) = Sum_{k = 1..n} 1/((2*k+1)*a(k)) < 1.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 2, 6, 31, 1527, 3509710, 19634198420529, 670572652324570519822017836, 444183929825540926086588009989665668909119960123355423
Offset: 1

Views

Author

N. J. A. Sloane, Sep 14 2024

Keywords

Crossrefs

A376056 Lexicographically earliest sequence of positive integers a(1), a(2), a(3), ... such that for any n > 0, S(n) = Sum_{k = 1..n} (2*k-1)/a(k) < 1.

Original entry on oeis.org

2, 7, 71, 6959, 62255215, 4736981006316791, 26518805245879857416837904442871, 811438882694890436523185183518581584358651922339197834228784351
Offset: 1

Views

Author

N. J. A. Sloane, Sep 14 2024

Keywords

Comments

Theorem: Given any sequence of nonnegative integers b(1), b(2), b(3), ..., let a(1), a(2), a(3), ... be the lexicographically earliest sequence of positive integers such that for all n >= 1, S(n) = Sum_{k = 1..n} b(k)/a(k) < 1. Then S(n) = (e(n)-1)/e(n) for positive integers e(1), e(2), e(3), ....
For the present sequence the e(k) are given in A376057.

Crossrefs

Programs

  • Maple
    # Given a sequence b(1), b(2), b(3), ... of nonnegative real numbers, this program computes the first M terms of the lexicographically earliest sequence of positive integers a(1), a(2), a(3), ... with the property that for any n > 0, S(n) = Sum_{k = 1..n} b(k)/a(k) < 1.
    # For the present sequence we set b(k) = 2*k - 1.
    b := Array(0..100,-1); a := Array(0..100,-1); S := Array(0..100,-1); d := Array(0..100,-1);
    for k from 1 to 100 do b[k]:=2*k-1; od:
    M:=8;
    S[0] := 0; d[0] := 1;
    for n from 1 to M do
    a[n] := floor(b[n]/d[n-1])+1;
    S[n] := S[n-1] + b[n]/a[n];
    d[n] := 1 - S[n];
    od:
    La:=[seq(a[n],n=1..M)]; # the present sequence
    Ls:=[seq(S[n],n=1..M)]; # the sums S(n)
    Lsn:=[seq(numer(S[n]),n=1..M)];
    Lsd:=[seq(denom(S[n]),n=1..M)]; # A376057
    Lsd-Lsn; # As a check, by the above theorem, this should (and does) produce the all-1's sequence
    # Some small changes to the program are needed if the starting sequence {b(n)} has offset 0, as for example in the case of the Fibonacci or Catalan numbers (see A376058-A376061).

Formula

a(n+1) = (2*n+1)*A376057(n) + 1.

A376053 Numerator of the sum S(n) defined in A376052.

Original entry on oeis.org

1, 8, 71, 248, 3043, 43024, 89051, 764441, 451021514, 25508567769, 411827311870583771, 525058386770138717020639964821, 528134692562568161116953143877712480332943632586669596859, 2267693117789905604207315326366543773113615946806750184592188584359364943382168221068055512231683584106110223751
Offset: 1

Views

Author

N. J. A. Sloane, Sep 14 2024

Keywords

Examples

			The initial values of S(n) are 1/3, 8/15, 71/105, 248/315, 3043/3465, 43024/45045, 89051/90090, ...
		

Crossrefs

A376054 Denominator of sum S(n) defined in A376052.

Original entry on oeis.org

3, 15, 105, 315, 3465, 45045, 90090, 765765, 451035585, 25508568085, 411827311870584610, 525058386770138717020639964850, 528134692562568161116953143877712480332943632586669596900
Offset: 1

Views

Author

N. J. A. Sloane, Sep 14 2024

Keywords

Examples

			The initial values of S(n) are 1/3, 8/15, 71/105, 248/315, 3043/3465, 43024/45045, 89051/90090, ...
		

Crossrefs

Showing 1-4 of 4 results.