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 1-5 of 5 results.

A376488 a(n) is the least k such that A375422(k) = n.

Original entry on oeis.org

1, 2, 4, 9, 13, 16, 18, 21, 71, 72, 75, 77, 79, 82, 84, 85, 88, 93, 95, 97, 470, 472, 475, 497, 500, 511, 515, 526, 529, 544, 557, 2618, 2738, 2743, 2744, 2749, 2761, 2762, 2827, 2832, 2835, 2862, 2890, 2892, 2895, 2896, 2901, 2902, 2910, 2932, 2938, 2955
Offset: 1

Views

Author

Rémy Sigrist, Sep 25 2024

Keywords

Comments

In other words, a(n) is the least k such that the set {(1, prime(1)), (2, prime(2)), ..., (k, prime(k))} contains n aligned points (where prime(k) denotes the k-th prime number).
Is this sequence infinite?

Crossrefs

Programs

  • PARI
    \\ See Links section.

A357345 E.g.f. satisfies A(x) = -log(1 - x * exp(A(x))) * exp(3 * A(x)).

Original entry on oeis.org

0, 1, 9, 173, 5226, 216564, 11429592, 733443990, 55447217928, 4826605609584, 475490102407200, 52299789903627408, 6353202640983827472, 844774875973448667792, 122040471544637793494760, 19034141943046836097099080, 3187643959565686909679931648
Offset: 0

Views

Author

Seiichi Manyama, Sep 25 2022

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=1, n, (n+3*k)^(k-1)*abs(stirling(n, k, 1)));

Formula

a(n) = Sum_{k=1..n} (n+3*k)^(k-1) * |Stirling1(n,k)|.
E.g.f.: Series_Reversion( exp(-x) * (1 - exp(-x * exp(-3*x))) ). - Seiichi Manyama, Sep 09 2024

A381110 a(n) is the maximum number of points from the set {(k, f(k)); k = 0..n} belonging to a straight line passing through the point (n, f(n)), where f(n) = A060143(n) = floor(n/phi) and phi is the golden ratio (sqrt(5)+1)/2.

Original entry on oeis.org

1, 2, 2, 2, 3, 3, 4, 3, 5, 3, 4, 4, 4, 5, 3, 5, 4, 4, 6, 4, 5, 5, 5, 6, 5, 6, 7, 6, 5, 6, 7, 6, 7, 5, 7, 8, 6, 8, 6, 7, 9, 6, 9, 7, 6, 10, 6, 7, 8, 7, 11, 7, 7, 9, 7, 12, 7, 8, 10, 8, 8, 8, 8, 11, 8, 9, 9, 9, 9, 8, 9, 10, 9, 10, 9, 10, 11, 8, 10, 10, 10, 11, 8
Offset: 0

Views

Author

Pontus von Brömssen, Feb 14 2025

Keywords

Comments

The sequence would remain the same if A060143 in the definition were replaced with A066096, i.e., if points (k, floor(k*phi)) were considered instead of (k, floor(k/phi)).

Crossrefs

A375423 a(1) = 1; for any n > 1, a(n) is the maximum number of points from the set {(k, a(k)), k = 1..n-1} belonging to a straight line passing through the point (n-1, a(n-1)).

Original entry on oeis.org

1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 3, 5, 5, 4, 4, 5, 3, 6, 4, 6, 3, 7, 5, 4, 7, 4, 8, 4, 9, 5, 5, 6, 4, 10, 6, 4, 11, 6, 5, 7, 3, 8, 3, 9, 4, 12, 3, 10, 4, 13, 3, 11, 5, 8, 3, 12, 6, 6, 7, 4, 14, 4, 15, 4, 16, 4, 17, 4, 18, 5, 9, 4, 19, 4, 20, 5, 10, 3, 13, 3
Offset: 1

Views

Author

Rémy Sigrist, Aug 14 2024

Keywords

Comments

This sequence is unbounded (if the sequence was bounded, say by m, then, by the pigeonhole principle, some value v <= m would appear infinitely many times, and for any k > 0, the k-th occurrence of v would be followed by a value >= k, a contradiction).

Examples

			The first terms, alongside an appropriate set of points, are:
  n   a(n)  Points
  --  ----  -----------------------------------
   1     1  N/A
   2     1  (1,1)
   3     2  (1,1), (2,1)
   4     2  (1,1), (3,2)
   5     2  (1,1), (4,2)
   6     3  (3,2), (4,2), (5,2)
   7     3  (2,1), (4,2), (6,3)
   8     3  (1,1), (4,2), (7,3)
   9     3  (2,1), (5,2), (8,3)
  10     4  (6,3), (7,3), (8,3), (9,3)
  11     4  (1,1), (4,2), (7,3), (10,4)
  12     4  (2,1), (5,2), (8,3), (11,4)
  13     3  (4,2), (8,3), (12,4)
  14     5  (6,3), (7,3), (8,3), (9,3), (13,3)
  15     5  (2,1), (5,2), (8,3), (11,4), (14,5)
		

Crossrefs

Programs

  • PARI
    \\ See Links section.

A376497 a(n) is the maximum number of points from the set {(prime(k), prime(k+1)), k = 1..n} belonging to a straight line passing through the point (prime(n), prime(n+1)) (where prime(k) denotes the k-th prime number).

Original entry on oeis.org

1, 2, 2, 2, 3, 2, 4, 3, 3, 5, 2, 4, 6, 5, 3, 4, 7, 5, 6, 8, 6, 7, 7, 3, 8, 9, 9, 10, 10, 3, 11, 8, 11, 3, 12, 9, 10, 12, 11, 12, 13, 3, 14, 13, 15, 3, 2, 14, 16, 15, 13, 17, 3, 14, 15, 16, 18, 17, 16, 19, 4, 4, 17, 20, 18, 3, 18, 5, 21, 19, 19, 3, 20, 21, 20
Offset: 1

Views

Author

Rémy Sigrist, Sep 25 2024

Keywords

Comments

Is this sequence unbounded?

Examples

			The first terms, alongside an appropriate set of points, are:
  n   a(n)  Points
  --  ----  ------------------------------------------------
   1     1  (2,3)
   2     2  (2,3), (3,5)
   3     2  (3,5), (5,7)
   4     2  (5,7), (7,11)
   5     3  (3,5), (5,7), (11,13)
   6     2  (7,11), (13,17)
   7     4  (3,5), (5,7), (11,13), (17,19)
   8     3  (7,11), (13,17), (19,23)
   9     3  (3,5), (13,17), (23,29)
  10     5  (3,5), (5,7), (11,13), (17,19), (29,31)
  11     2  (23,29), (31,37)
  12     4  (7,11), (13,17), (19,23), (37,41)
  13     6  (3,5), (5,7), (11,13), (17,19), (29,31), (41,43)
  14     5  (7,11), (13,17), (19,23), (37,41), (43,47)
  15     3  (23,29), (31,37), (47,53)
  16     4  (23,29), (31,37), (47,53), (53,59)
		

Crossrefs

Cf. A375422.

Programs

  • PARI
    \\ See Links section.
Showing 1-5 of 5 results.