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 1-10 of 11 results. Next

A011538 Numbers that contain an 8.

Original entry on oeis.org

8, 18, 28, 38, 48, 58, 68, 78, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 98, 108, 118, 128, 138, 148, 158, 168, 178, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 198, 208, 218, 228, 238, 248, 258, 268, 278, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289
Offset: 1

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Comments

In China, numbers with many 8 digits are considered auspicious because the character for 8 (八) sounds like the character for wealth (發). - Charles R Greathouse IV, Aug 28 2012

Crossrefs

Supersequence of A043521.

Programs

Formula

a(n) ~ n. - Charles R Greathouse IV, Aug 28 2012

A043489 Numbers having one 0 in base 10.

Original entry on oeis.org

0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 120, 130, 140, 150, 160, 170, 180, 190, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 220, 230, 240, 250, 260, 270, 280, 290, 301, 302, 303
Offset: 1

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Comments

From Hieronymus Fischer, May 28 2014: (Start)
Inversion:
Given a term m, the index n such that a(n) = m can be calculated by the following procedure [see Prog section with an implementation in Smalltalk]. With k := floor(log_10(m)), z = digit position of the '0' in m counted from the right (starting with 0).
Case 1: A043489_inverse(m) = 1 + Sum_{j=1..k} A052382_inverse(floor(m/10^j))*9^(j-1), if z = 0.
Case 2: A043489_inverse(m) = 1 + A043489_inverse(m - c - m mod 10^z) + A052382_inverse(m mod 10^z)) - (9^z - 1)/8, if z > 0, where c := 1, if the digit at position z+1 of m is ‘1’ and k > z + 1, otherwise c := 10.
Example 1: m = 990, k = 2, z = 0 (Case 1), A043489_inverse(990) = 1 + A052382_inverse(99))*1 + A052382_inverse(9))*9 = 1 + 90 + 81 = 172.
Example 2: m = 1099, k = 3, z = 2 (Case 2), A043489_inverse(1099) = 1 + A043489_inverse(990) + A052382_inverse(99)) - 10 = 1 + A043489_inverse(990) + 80 = 1 + 172 + 80 = 253.
(End)

Examples

			a(10^1)= 90.
a(10^2)= 590.
a(10^3)= 4190.
a(10^4)= 35209.
a(10^5)= 308949.
a(10^6)= 2901559.
a(10^7)= 27250269.
a(10^8)= 263280979.
a(10^9)= 2591064889.
a(10^10)= 25822705899.
a(10^20)= 366116331598324670219.
a(10^50)= 3.7349122484477433715662812...*10^51
a(10^100)= 4.4588697999177752943575344...*10^103.
a(10^1000)= 5.5729817962143143812258616...*10^1045.
[Examples by _Hieronymus Fischer_, May 28 2014]
		

Crossrefs

Programs

  • Mathematica
    Select[Range[0,9000],DigitCount[#,10,0]==1&] (* Enrique Pérez Herrero, Nov 29 2013 *)
  • PARI
    is(n)=#select(d->d==0, digits(n))==1 \\ Charles R Greathouse IV, Oct 06 2016
  • Smalltalk
    A043489_nextTerm
      "Answers the minimal number > m which contains exactly 1 zero digit (in base 10), where m is the receiver.
      Usage: a(n) A043489_nextTerm
      Answer: a(n+1)"
      | d d0 s n p |
      n := self.
      p := 1.
      s := n.
      (d0 := n // p \\ 10) = 0
         ifTrue:
              [p := 10 * p.
              s := s + 1].
      [(d := n // p \\ 10) = 9] whileTrue:
              [s := s - (8 * p).
              p := 10 * p].
      (d = 0 or: [d0 = 0]) ifTrue: [s := s - (p // 10)].
      ^s + p
    [by Hieronymus Fischer, May 28 2014]
    ------------------
    
  • Smalltalk
    A043489
    "Answers the n-th number such that number of 0's in base 10 is 1, where n is the receiver. Uses the method zerofree: base from A052382.
      Usage: n A043489
      Answer: a(n)"
      | n a b dj cj gj ej j r |
      n := self.
      n <= 1 ifTrue: [^r := 0].
      n <= 10 ifTrue: [^r := (n - 1) * 10].
      j := n invGeometricSum2: 9.
      b := j geometricSum2: 9.
      cj := 9 ** j.
      dj := (j + 1) * cj.
      gj := (cj - 1) / 8.
      ej := 10 ** j.
      a := n - b - 2.
      b := a \\ dj.
      r := (a // dj + 1) * ej * 10.
      [b >= cj] whileTrue:
              [a := b - cj.
              cj := cj // 9.
              dj := j * cj.
              b := a \\ dj.
              r := (a // dj + 1) * ej + r.
              gj := gj - cj.
              ej := ej // 10.
              j := j - 1].
      r := (b + gj zerofree: 10) + r.
      ^r
    [by Hieronymus Fischer, May 28 2014]
    ------------------
    
  • Smalltalk
    A043489_inverse
      "Answers the index n such that A043489(n) = m, where m is the receiver. Uses A052382_inverse from A052382.
      Usage: n zerofree_inverse: b [b = 10 for this sequence]
      Answer: a(n)"
      | m p q s r m1 mr |
      m := self.
      m < 100 ifTrue: [^m // 10 + 1].
      p := q := 1.
      s := 0.
      [m // p \\ 10 = 0] whileFalse:
         [p := 10 * p.
         s := s + q.
         q := 9 * q].
      p > 1
         ifTrue:
         [r := m \\ p.
         p := 10 * p.
         m1 := m // p.
         (m1 \\ 10 = 1 and: [m1 > 10])
              ifTrue: [mr := m - r - 1]
              ifFalse: [mr := m - r - 10].
         ^mr A043489_inverse + r A052382_inverse - s + 1]
         ifFalse:
         [s := 1.
         p := 10.
         q := 1.
         [p < m] whileTrue:
              [s := (m // p) A052382_inverse * q + s.
              p := 10 * p.
              q := 9 * q].
         ^s]
    [by Hieronymus Fischer, May 28 2014]
    

Formula

From Hieronymus Fischer, May 28 2014: (Start)
a(1 + Sum_{j=1..n} j*9^j) = 10*(10^n - 1).
a(2 + Sum_{j=1..n} j*9^j) = 10^(n+1) + (10^n - 1)/9 = (91*10^n - 1)/9.
a((9^(n+1) - 1)/8 + 1 + Sum_{j=1..n} j*9^j) = 10*(10^(n+1) - 1)/9, where Sum_{j=1..n} j*9^j = (1-(n+1)*9^n+n*9^(n+1))*9/64.
Iterative calculation:
With i := digit position of the '0' in a(n) counted from the right (starting with 0), j = number of contiguous '9' digits in a(n) counted from position 1, if i = 0, and counted from position 0, if i > 0 (0 if none)
a(n+1) = a(n) + 10 + (10^j - 1)/9, if i = 0.
a(n+1) = a(n) + 1 + (10^(j-1) - 1)/9, if i = j > 0.
a(n+1) = a(n) + 1 + (10^j - 1)/9, if i > j.
[see Prog section for an implementation in Smalltalk].
Direct calculation:
Set j := max( m | (Sum_{i=1..m} i*9^i) < n) and c(1) := n - 2 - Sum_{i=1..j} i*9^i. Define successively,
c(i+1) = c(i) mod ((j-i+2)*9^(j-i+1)) - 9^(j-i+1) while this value is >= 0, and set k := i for the last such index for which c(i) >= 0.
Then a(n) = A052382(c(k) mod ((j-k+2)*9^(j-k+1)) + (9^(j-k+1)-1)/8) + Sum_{i=1..k} ((floor(c(i)/((j-i+2)*9^(j-i+1))) + 1) * 10^(j-i+2)). [see Prog section for an implementation in Smalltalk].
Behavior for large n:
a(n) = O(n^(log(10)/log(9))/log(n)).
a(n) = O(n^1.047951651.../log(n)).
Inequalities:
a(n) < 2*(8n)^log_9(10)/(log_9(8n)*log_9(10)).
a(n) < (8n)^log_9(10)/(log_9(8n)*log_9(10)), for large n (n > 10^50).
a(n) > 0.9*(8n)^log_9(10)/(log_9(8n)*log_9(10)), for 2 < n < 10^50.
a(n) >= A011540(n), equality holds for n <= 10.
(End)

A043493 Numbers that contain a single 1.

Original entry on oeis.org

1, 10, 12, 13, 14, 15, 16, 17, 18, 19, 21, 31, 41, 51, 61, 71, 81, 91, 100, 102, 103, 104, 105, 106, 107, 108, 109, 120, 122, 123, 124, 125, 126, 127, 128, 129, 130, 132, 133, 134, 135, 136, 137, 138, 139, 140, 142, 143, 144, 145
Offset: 1

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Programs

Formula

a(n) >> n^k where k = log(10)/log(9) = 1.04795.... - Charles R Greathouse IV, Jan 21 2025

A043509 Numbers having exactly one 5 in base 10.

Original entry on oeis.org

5, 15, 25, 35, 45, 50, 51, 52, 53, 54, 56, 57, 58, 59, 65, 75, 85, 95, 105, 115, 125, 135, 145, 150, 151, 152, 153, 154, 156, 157, 158, 159, 165, 175, 185, 195, 205, 215, 225, 235, 245, 250, 251, 252, 253, 254, 256, 257, 258, 259
Offset: 1

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Programs

Formula

a(n) ≍ n^k log n, with k = log 9/log 10 = 0.9542425... = A104139. - Charles R Greathouse IV, Nov 01 2022

A043513 Numbers having one 6 in base 10.

Original entry on oeis.org

6, 16, 26, 36, 46, 56, 60, 61, 62, 63, 64, 65, 67, 68, 69, 76, 86, 96, 106, 116, 126, 136, 146, 156, 160, 161, 162, 163, 164, 165, 167, 168, 169, 176, 186, 196, 206, 216, 226, 236, 246, 256, 260, 261, 262, 263, 264, 265, 267, 268
Offset: 1

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Crossrefs

Programs

  • Mathematica
    Select[Range[300],DigitCount[#,10,6]==1&] (* Harvey P. Dale, Aug 15 2011 *)

A043497 Numbers having one 2 in base 10.

Original entry on oeis.org

2, 12, 20, 21, 23, 24, 25, 26, 27, 28, 29, 32, 42, 52, 62, 72, 82, 92, 102, 112, 120, 121, 123, 124, 125, 126, 127, 128, 129, 132, 142, 152, 162, 172, 182, 192, 200, 201, 203, 204, 205, 206, 207, 208, 209, 210, 211, 213, 214, 215
Offset: 1

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A043501 Numbers having one 3 in base 10.

Original entry on oeis.org

3, 13, 23, 30, 31, 32, 34, 35, 36, 37, 38, 39, 43, 53, 63, 73, 83, 93, 103, 113, 123, 130, 131, 132, 134, 135, 136, 137, 138, 139, 143, 153, 163, 173, 183, 193, 203, 213, 223, 230, 231, 232, 234, 235, 236, 237, 238, 239, 243, 253
Offset: 1

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Programs

A043505 Numbers having one 4 in base 10.

Original entry on oeis.org

4, 14, 24, 34, 40, 41, 42, 43, 45, 46, 47, 48, 49, 54, 64, 74, 84, 94, 104, 114, 124, 134, 140, 141, 142, 143, 145, 146, 147, 148, 149, 154, 164, 174, 184, 194, 204, 214, 224, 234, 240, 241, 242, 243, 245, 246, 247, 248, 249, 254
Offset: 1

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Programs

A043517 Numbers having one 7 in base 10.

Original entry on oeis.org

7, 17, 27, 37, 47, 57, 67, 70, 71, 72, 73, 74, 75, 76, 78, 79, 87, 97, 107, 117, 127, 137, 147, 157, 167, 170, 171, 172, 173, 174, 175, 176, 178, 179, 187, 197, 207, 217, 227, 237, 247, 257, 267, 270, 271, 272, 273, 274, 275, 276
Offset: 1

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Programs

  • Mathematica
    Select[Range[9000],DigitCount[#,10,7]==1&]

A043525 Numbers having one 9 in base 10.

Original entry on oeis.org

9, 19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 109, 119, 129, 139, 149, 159, 169, 179, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 209, 219, 229, 239, 249, 259, 269, 279, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 309, 319
Offset: 1

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Crossrefs

Programs

  • Mathematica
    Select[Range[300],DigitCount[#,10,9]==1&] (* Harvey P. Dale, Jan 19 2013 *)
  • Python
    def ok(n): return str(n).count('9') == 1
    print(list(filter(ok, range(320)))) # Michael S. Branicky, Sep 19 2021

Formula

Sum_{n>=1} 1/a(n) = A140502. - Amiram Eldar, Nov 14 2020
Showing 1-10 of 11 results. Next