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.

A067012 Absolute composites: every permutation of digits (dropping any leading zeros) is a composite number.

Original entry on oeis.org

4, 6, 8, 9, 12, 15, 18, 21, 22, 24, 25, 26, 27, 28, 33, 36, 39, 40, 42, 44, 45, 46, 48, 49, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 72, 75, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 93, 94, 96, 99, 102, 105, 108, 111, 114, 116, 117, 120, 122, 123
Offset: 1

Views

Author

Lior Manor, Dec 26 2001

Keywords

Examples

			18 is a term since it is composite and the permutation 81 is composite too.
		

Crossrefs

Subsequence of A067013.

Programs

  • Mathematica
    t={}; Do[l1=Table[FromDigits[k], {k,Permutations[IntegerDigits[n]]}]; If[Select[l1,PrimeQ] == {} && FreeQ[l1,1] == True, AppendTo[t,n]],{n,123}]; t  (* Jayanta Basu, May 03 2013  *)

A096600 Numbers such that in decimal representation all permutations of digits are nonsquares.

Original entry on oeis.org

2, 3, 5, 6, 7, 8, 11, 12, 13, 14, 15, 17, 19, 20, 21, 22, 23, 24, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 47, 48, 50, 51, 53, 54, 55, 56, 57, 58, 59, 60, 62, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 82, 83, 84, 85, 86, 87
Offset: 1

Views

Author

Reinhard Zumkeller, Jun 29 2004

Keywords

Comments

A062892(a(n)) = 0.

Examples

			134=2*67, 143=11*13, 314=2*157, 341=11*31, 413=7*59 and 431=A000040(83), therefore 134, 143, 314, 341, 413 and 431 are terms.
		

Crossrefs

Programs

  • Mathematica
    Select[Range[100],NoneTrue[Sqrt[#]&/@(FromDigits/@Permutations[IntegerDigits[ #]]),IntegerQ]&] (* Harvey P. Dale, Dec 04 2022 *)

A228096 Numbers consisting of only odd digits such that no permutation of its digits yields a prime.

Original entry on oeis.org

1, 9, 15, 33, 39, 51, 55, 57, 75, 77, 93, 99, 111, 117, 135, 153, 155, 159, 171, 177, 195, 315, 333, 339, 351, 355, 357, 375, 393, 399, 513, 515, 519, 531, 535, 537, 551, 553, 555, 559, 573, 579, 591, 595, 597, 711, 717, 735, 753, 759, 771, 777, 795
Offset: 1

Views

Author

Jayanta Basu, Aug 10 2013

Keywords

Comments

Apart from the first term, A061810 is a subsequence. Conjecture: a(n) ~ A061810(n). - Charles R Greathouse IV, Feb 15 2017

Examples

			51 is a member since it consists of only odd digits and both 15 and 51 are composites.
		

Crossrefs

Subsequence of A067013.

Programs

  • Mathematica
    Select[Range[800], And @@ OddQ[x = IntegerDigits[#]] && Count[FromDigits /@ Permutations[x], _?PrimeQ] == 0 &]
    Table[FromDigits/@Select[Tuples[Range[1,9,2],n],NoneTrue[FromDigits/@ Permutations[#],PrimeQ]&],{n,3}]//Flatten (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 09 2019 *)

A248010 Non-primatic permutable numbers: All permutations of the number's digits except the ones resulting in leading zeros are nonprimes.

Original entry on oeis.org

1, 4, 6, 8, 9, 10, 12, 15, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 33, 36, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 75, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 93, 94, 96, 99, 100, 102, 105, 108, 111, 114, 116, 117, 120, 122, 123, 126, 129, 132, 135, 138, 141, 144, 147
Offset: 1

Views

Author

Andreas Boe, Sep 29 2014

Keywords

Comments

This sequence differs slightly from "absolute composite numbers". 30 is not an absolute composite since 03 is counted as a prime, but in this sequence permutations with leading zeros are disqualified as viable permutations.

Examples

			7000 qualifies since it is a composite and the only allowed permutation of its four digits.
		

Crossrefs

Absolute composites: A067012, A067013.
Monoprimatic permutable numbers: A245808.
Biprimatic permutable numbers: A246043.

A225438 Odd numbers such that no permutation of its digits yields a prime.

Original entry on oeis.org

1, 9, 15, 21, 25, 27, 33, 39, 45, 49, 51, 55, 57, 63, 65, 69, 75, 77, 81, 85, 87, 93, 99, 105, 111, 117, 123, 129, 135, 141, 147, 153, 155, 159, 161, 165, 171, 177, 183, 185, 187, 189, 195, 201, 205, 207, 213, 219, 221, 225, 231, 237, 243, 245, 247, 249
Offset: 1

Views

Author

Jayanta Basu, May 08 2013

Keywords

Comments

Subset of A067013.

Examples

			105 is a member since none of 105, 150, 15, 51, 510, 501 is a prime.
		

Crossrefs

Cf. A067013.

Programs

  • Mathematica
    t={}; Do[If[Length[Select[Table[FromDigits[k], {k,Permutations[IntegerDigits[n]]}],PrimeQ]]==0, AppendTo[t,n]], {n,1,250,2}]; t
Showing 1-5 of 5 results.