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.

A089346 Primes of the form identical odd digits followed by a 1.

Original entry on oeis.org

11, 31, 71, 331, 991, 3331, 33331, 99991, 333331, 3333331, 9999991, 33333331, 555555555551, 5555555555551, 7777777777771, 333333333333333331, 1111111111111111111, 77777777777777777771, 11111111111111111111111
Offset: 1

Views

Author

Amarnath Murthy, Nov 05 2003

Keywords

Links

Crossrefs

Cf. A089345, A089347.

Programs

  • Mathematica
    Select[FromDigits/@Flatten[Table[Join[PadLeft[{n},i,n],{1}],{i,25},{n,1,9,2}], 1],PrimeQ] (* Harvey P. Dale, Jul 25 2011 *)

Extensions

More terms from Ray Chandler, Nov 07 2003

A089345 Primes of the form identical even digits followed by a 1.

Original entry on oeis.org

41, 61, 661, 881, 2221, 4441, 6661, 6666666661, 44444444441, 222222222222222221, 666666666666666661, 8888888888888888881, 666666666666666666661, 6666666666666666666661, 4444444444444444444444444441
Offset: 1

Views

Author

Amarnath Murthy, Nov 05 2003

Keywords

Links

Crossrefs

Cf. A089346, A089347.

Programs

  • Mathematica
    Select[FromDigits/@Flatten[Table[Join[PadLeft[{n},i,n],{1}],{i,100},{n,2,9,2}],1],PrimeQ] (* Vincenzo Librandi, Dec 12 2011 *)

Extensions

More terms from Ray Chandler, Nov 07 2003

A109548 Primes of the form aaaa...aa1 where a is 1, 2, 3, 4 or 5.

Original entry on oeis.org

11, 31, 41, 331, 2221, 3331, 4441, 33331, 333331, 3333331, 33333331, 44444444441, 555555555551, 5555555555551, 222222222222222221, 333333333333333331, 1111111111111111111, 11111111111111111111111
Offset: 1

Views

Author

Roger L. Bagula, Jun 26 2005

Keywords

Links

Crossrefs

Cf. A051200, A004022, A093176, A093177, A089346, A093174, A092571, A089345, A089347.

Programs

  • Mathematica
    d[n_] = Mod[n, 6] a = Flatten[Table[Sum[d[k]*10^i, {i, 1, m}] + 1, {m, 1, 50}, {k, 1, 5}]] b = Flatten[Table[If[PrimeQ[a[[i]]] == True, a[[i]], {}], {i, 1, Length[a]}]]
Select[FromDigits/@Flatten[Table[PadLeft[{1},i,#]&/@{1,2,3,4,5},{i,2,80}],1],PrimeQ[#]&] (* Vincenzo Librandi, Dec 12 2011 *)

Formula

d=1, 2, 3, 4, 5 a(n) = if prime then Sum[d*10^i, {i, 1, m}] + 1

A109549 Primes of the form aaaa...aa1 where a is 6, 7, 8 or 9.

Original entry on oeis.org

61, 71, 661, 881, 991, 6661, 99991, 9999991, 6666666661, 7777777777771, 666666666666666661, 8888888888888888881, 77777777777777777771, 666666666666666666661, 6666666666666666666661, 77777777777777777777771
Offset: 1

Views

Author

Roger L. Bagula, Jun 26 2005

Keywords

Comments

Easy-to-remember large primes can be formed in this manner.

Links

Crossrefs

Cf. A051200, A004022, A093176, A093177, A089346, A093174, A092571, A089345, A089347.

Programs

  • Mathematica
    d[n_] = If[5 + Mod[n, 6] > 0, 5 + Mod[n, 6], 1] a = Flatten[Table[Sum[d[k]*10^i, {i, 1, m}] + 1, {m, 1, 50}, {k, 1, 4}]] b = Flatten[Table[If[PrimeQ[a[[i]]] == True, a[[i]], {}], {i, 1, Length[a]}]]
Select[FromDigits/@Flatten[Table[PadLeft[{1},i,#]&/@{6,7,8,9},{i,2,100}],1],PrimeQ[#]&] (* Vincenzo Librandi, Dec 12 2011 *)

Formula

d=6, 7, 8, 9 a(n) = if prime then Sum[d*10^i, {i, 1, m}] + 1

A109550 Primes of the form aaaa...aa1 where a is 3, 4, 5, 6 or 7.

Original entry on oeis.org

31, 41, 61, 71, 331, 661, 3331, 4441, 6661, 33331, 333331, 3333331, 33333331, 6666666661, 44444444441, 555555555551, 5555555555551, 7777777777771, 333333333333333331, 666666666666666661, 77777777777777777771
Offset: 1

Views

Author

Roger L. Bagula, Jun 26 2005

Keywords

Links

Crossrefs

Cf. A051200, A004022, A093176, A093177, A089346, A093174, A092571, A089345, A089347.

Programs

  • Mathematica
    d[n_] = If[2 + Mod[n, 6] > 0, 2 + Mod[n, 6], 1] a = Flatten[Table[Sum[d[k]*10^i, {i, 1, m}] + 1, {m, 1, 50}, {k, 1, 4}]] b = Flatten[Table[If[PrimeQ[a[[i]]] == True, a[[i]], {}], {i, 1, Length[a]}]]
Select[FromDigits/@Flatten[Table[PadLeft[{1},i,#]&/@{3,4, 5,6,7},{i,2,100}],1],PrimeQ[#]&] (* Vincenzo Librandi, Dec 12 2011 *)

Formula

d=3, 4, 5, 6, 7 a(n) = if prime then Sum[d*10^i, {i, 1, m}] + 1
Showing 1-5 of 5 results.

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