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 1-7 of 7 results.

A217394 Numbers starting with 2.

Original entry on oeis.org

2, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242
Offset: 1

Views

Author

Jeremy Gardiner, Oct 02 2012

Keywords

Comments

The lower and upper asymptotic densities of this sequence are 1/18 and 10/27, respectively. - Amiram Eldar, Feb 27 2021

Links

Crossrefs

Cf. A006092, A011532.
Subsequences include: A045708, A045726, A077327, A077678, A106412, A106422.
Cf. A131835, A217395, A217397, A217398, A217399, A217400, A217401, A217402.

Programs

  • Mathematica
    Select[Range[300], IntegerDigits[#][[1]] == 2 &] (* T. D. Noe, Oct 02 2012 *)
  • Python
    def agen():
  yield 2
  digits, adder = 1, 20
  while True:
    for i in range(10**digits): yield adder + i
    digits, adder = digits+1, adder*10
g = agen()
print([next(g) for i in range(54)]) # Michael S. Branicky, Feb 20 2021
  • Python
    def A217394(n): return n+(17*10**(len(str(9*n-8))-1))//9 # Chai Wah Wu, Dec 07 2024

Formula

a(n) = n + (17*10^floor(log_10(9*n-8))-8)/9. - Alan Michael Gómez Calderón, May 15 2023

A217395 Numbers starting with 3.

Original entry on oeis.org

3, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 340, 341, 342
Offset: 1

Views

Author

Jeremy Gardiner, Oct 02 2012

Keywords

Comments

The lower and upper asymptotic densities of this sequence are 1/27 and 5/18, respectively. - Amiram Eldar, Feb 27 2021

Links

Crossrefs

Cf. A006092, A011533.
Subsequences include: A045709, A077328, A077679, A106413, A106423.
Cf. A131835, A217394, A217397, A217398, A217399, A217400, A217401, A217402.

Programs

  • Mathematica
    Select[Range[1000], IntegerDigits[#][[1]] == 3 &] (* T. D. Noe, Oct 02 2012 *)
  • PARI
    a(n) = n + 26*10^logint(9*n,10)\9; \\ Kevin Ryde, Mar 30 2021
  • Python
    def agen():
  yield 3
  digits, adder = 1, 30
  while True:
    for i in range(10**digits): yield adder + i
    digits, adder = digits+1, adder*10
g = agen()
print([next(g) for i in range(54)]) # Michael S. Branicky, Mar 30 2021
  • Python
    def A217395(n): return n+26*10**(len(str(9*n-8))-1)//9 # Chai Wah Wu, Sep 11 2024

Formula

a(n) = n + (26*10^floor(log_10(9*n-8))-8)/9. - Alan Michael Gómez Calderón, May 16 2023

A000867 Numbers beginning with letter 'f' in English.

Original entry on oeis.org

4, 5, 14, 15, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

Links

Crossrefs

Subsequence of A125299.
Cf. A000865, A000870, A000873, A000981, A006092.

Programs

  • Mathematica
    Select[Range[1000], First[Characters[IntegerName[#,"Words"]]]=="f"&] (* James C. McMahon, Dec 11 2023 *)

Extensions

More terms from John Cerkan, Feb 11 2017

A000870 Numbers beginning with letter 's' in English.

Original entry on oeis.org

6, 7, 16, 17, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 600, 601, 602, 603, 604, 605, 606, 607, 608, 609, 610, 611, 612, 613, 614, 615, 616, 617, 618, 619, 620
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

Links

Crossrefs

Subsequence of A125299.
Cf. A000865, A000867, A000873, A000981, A006092.

Programs

  • Mathematica
    Select[Range[10^3], Function[d, Or[And[Mod[IntegerLength@ #, 3] == 2, MemberQ[{16, 17}, FromDigits@ Take[d, 2]]], MemberQ[{6, 7}, First@ d]]]@ IntegerDigits@ # &] (* Michael De Vlieger, Feb 13 2017 *)

Extensions

Edited by John Cerkan, Feb 13 2017

A000873 Numbers beginning with letter 'e' in English.

Original entry on oeis.org

8, 11, 18, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 800, 801, 802, 803, 804, 805, 806, 807, 808, 809, 810, 811, 812, 813, 814, 815, 816, 817, 818, 819, 820, 821, 822, 823, 824, 825, 826, 827, 828, 829
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

Links

Crossrefs

Subsequence of A000852.
Cf. A000865, A000867, A000870, A000981, A006092.

Programs

  • Mathematica
    Select[Range[10^3], Function[d, Or[And[Mod[IntegerLength@ #, 3] == 2, MemberQ[{11, 18}, FromDigits@ Take[d, 2]]], First@ d == 8]]@ IntegerDigits@ # &] (* Michael De Vlieger, Feb 13 2017 *)

Extensions

Corrected by Sam Alexander (pink2001x(AT)hotmail.com)
Edited by John Cerkan, Feb 13 2017

A000981 Numbers beginning with letter 'n' in English.

Original entry on oeis.org

9, 19, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 900, 901, 902, 903, 904, 905, 906, 907, 908, 909, 910, 911, 912, 913, 914, 915, 916, 917, 918, 919, 920, 921, 922, 923, 924, 925, 926, 927, 928, 929, 930
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

Links

Crossrefs

Subsequence of A125299.
Cf. A000865, A000867, A000870, A000873, A006092.

Programs

  • Mathematica
    Select[Range[10^3], Function[d, Or[And[Mod[IntegerLength@ #, 3] == 2, FromDigits@ Take[d, 2] == 19], First@ d == 9]]@ IntegerDigits@ # &] (* Michael De Vlieger, Feb 13 2017 *)

Extensions

Edited by John Cerkan, Feb 13 2017

A130842 Positive even integers that start with the letter 't' .

Original entry on oeis.org

2, 10, 12, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 200, 202, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244, 246, 248, 250, 252, 254, 256, 258, 260, 262, 264, 266, 268, 270, 272, 274, 276, 278, 280, 282
Offset: 1

Views

Author

Joohwan Lee (modularform(AT)yahoo.com), Jul 20 2007

Keywords

Formula

Equals A006092 INTERSECT A005843. - R. J. Mathar, Jul 22 2007

Extensions

Corrected and extended by R. J. Mathar, Jul 22 2007
Showing 1-7 of 7 results.

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

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