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.

Previous Showing 11-18 of 18 results.

A262581 Concatenation of the numbers from 1 to n but omitting 11.

Original entry on oeis.org

1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891012, 123456789101213, 12345678910121314, 1234567891012131415, 123456789101213141516, 12345678910121314151617, 1234567891012131415161718, 123456789101213141516171819, 12345678910121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

There are only two primes among the first 98 terms, namely 123456789101213 and
1234567891012131415161718192021222324252627282930313233343536\
373839404142434445464748495051525354555657585960616263.
Does this sequence contain any other primes?
No other primes through a(10000). - Robert Price, Nov 05 2018

Crossrefs

Cf. A007908, A262299, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {11}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)
  • PARI
    terms(n) = my(s="", i=0); for(k=1, n, if(k!=11, s=concat(s, Str(k)); print1(eval(s), ", "); i++); if(i==n, break))
/* Print initial 20 terms as follows */
terms(20) \\ Felix Fröhlich, Nov 05 2018

A262573 Concatenation of the numbers from 1 to n but omitting 3.

Original entry on oeis.org

1, 12, 124, 1245, 12456, 124567, 1245678, 12456789, 1245678910, 124567891011, 12456789101112, 1245678910111213, 124567891011121314, 12456789101112131415, 1245678910111213141516, 124567891011121314151617, 12456789101112131415161718, 1245678910111213141516171819, 124567891011121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

The only prime among the first 98 terms is a(6) = 124567. Does the sequence contain any other primes?
No other primes through a(10000). - Robert Price, Nov 04 2018

Crossrefs

Cf. A007908, A262299, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {3}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)
Join[{1,12},Table[FromDigits[Join[{1,2},Flatten[IntegerDigits/@Range[4,n]]]],{n,4,20}]] (* Harvey P. Dale, Sep 17 2019 *)

A262574 Concatenation of the numbers from 1 to n but omitting 4.

Original entry on oeis.org

1, 12, 123, 1235, 12356, 123567, 1235678, 12356789, 1235678910, 123567891011, 12356789101112, 1235678910111213, 123567891011121314, 12356789101112131415, 1235678910111213141516, 123567891011121314151617, 12356789101112131415161718, 1235678910111213141516171819, 123567891011121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

The only prime among the first 98 terms is a(8) = 12356789. Does the sequence contain any other primes?
No other primes through a(10000). - Robert Price, Nov 03 2018

Crossrefs

Cf. A007908, A262299, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {4}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)

A262576 Concatenation of the numbers from 1 to n but omitting 6.

Original entry on oeis.org

1, 12, 123, 1234, 12345, 123457, 1234578, 12345789, 1234578910, 123457891011, 12345789101112, 1234578910111213, 123457891011121314, 12345789101112131415, 1234578910111213141516, 123457891011121314151617, 12345789101112131415161718, 1234578910111213141516171819, 123457891011121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

The only prime among the first 98 terms is a(6) = 123457. Does the sequence contain any other primes?
No additional primes through the first 2000 terms. - Harvey P. Dale, Sep 27 2018
Differs from A132943 at about the 28th terms.
No primes, other than a(6), through a(10000). - Robert Price, Nov 03 2018

Crossrefs

Cf. A132943.
Cf. A007908, A262299, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    Module[{nn=20,c},c=Drop[Range[nn],{6}];Table[FromDigits[Flatten[ IntegerDigits/@ Take[c,n]]],{n,nn-1}]] (* Harvey P. Dale, Sep 27 2018 *)

A262577 Concatenation of the numbers from 1 to n but omitting 7.

Original entry on oeis.org

1, 12, 123, 1234, 12345, 123456, 1234568, 12345689, 1234568910, 123456891011, 12345689101112, 1234568910111213, 123456891011121314, 12345689101112131415, 1234568910111213141516, 123456891011121314151617, 12345689101112131415161718, 1234568910111213141516171819, 123456891011121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

There are only three primes among the first 98 terms: 123456891011,
12345689101112131415161718192021222324252627282930313233343536373839, and
12345689101112131415161718192021222324252627282930313233343536373839\
40414243444546474849505152535455565758596061626364566676869707172737\
475767778798081828384858687.
Does the sequence contain any other primes?
Yes, PARI reports the next (probable) prime after appending 13097; it has 54655 digits. - Bill McEachen, Oct 13 2015

Crossrefs

Cf. A007908, A262299, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    DeleteDuplicates@ Table[If[n >= 7, FromDigits@ Delete[Flatten[IntegerDigits /@ Range[n + 1]], 7], FromDigits@ Flatten[IntegerDigits /@ Range@ n]], {n, 19}] (* Michael De Vlieger, Oct 13 2015 *)

Formula

(a(n) - a(n-1)) mod 2 = 0 only for n=7. - Altug Alkan, Oct 15 2015

A262578 Concatenation of the numbers from 1 to n but omitting 8.

Original entry on oeis.org

1, 12, 123, 1234, 12345, 123456, 1234567, 12345679, 1234567910, 123456791011, 12345679101112, 1234567910111213, 123456791011121314, 12345679101112131415, 1234567910111213141516, 123456791011121314151617, 12345679101112131415161718, 1234567910111213141516171819, 123456791011121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

The first (probable) prime in this sequence is a(1872) = 1234567910111213...1873 (ending at 1873), a 6384-digit probable prime, too large to display here. It was found by David Broadhurst on Sep 27 2015.
No other primes through a(10000). - Robert Price, Nov 04 2018
a(1872) is prime. - Jason Yuen, Nov 17 2024

Crossrefs

Cf. A007908, A262299, A262300, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    Module[{nn=30, c}, c=Drop[Range[nn], {8}]; Table[FromDigits[Flatten[IntegerDigits/@Take[c, n]]], {n, nn-1}]] (* Vincenzo Librandi, Nov 05 2018 *)

A262579 Concatenation of the numbers from 1 to n but omitting 9.

Original entry on oeis.org

1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 1234567810, 123456781011, 12345678101112, 1234567810111213, 123456781011121314, 12345678101112131415, 1234567810111213141516, 123456781011121314151617, 12345678101112131415161718, 1234567810111213141516171819, 123456781011121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

There are only two primes among the first 98 terms, namely
1234567810111213141516171819 and 1234567810111213141516171819202122232425262728293031323334353637.
Does this sequence contain any other primes?
No other primes through a(10000). - Robert Price, Nov 04 2018

Crossrefs

Cf. A007908, A262299, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {9}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)
Module[{nn=20,c},c=Drop[Range[nn],{9}];Table[FromDigits[Flatten[ IntegerDigits/@ Take[c,n]]],{n,nn-1}]] (* Harvey P. Dale, Nov 30 2019 *)

A262580 Concatenation of the numbers from 1 to n but omitting 10.

Original entry on oeis.org

1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678911, 1234567891112, 123456789111213, 12345678911121314, 1234567891112131415, 123456789111213141516, 12345678911121314151617, 1234567891112131415161718, 123456789111213141516171819, 12345678911121314151617181920
Offset: 1

Views

Author

N. J. A. Sloane, Sep 25 2015

Keywords

Comments

The smallest prime in this sequence is the 61457-digit (probable) prime a(14512) = 123456789111213...14513 found by David Broadhurst on Sep 28 2015.

Crossrefs

Cf. A007908, A262299, A262571-A262582.
See A262300 for more about this problem.

Programs

  • Mathematica
    DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {10}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)
Previous Showing 11-18 of 18 results.

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

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