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 17 results. Next

A052033 Primes base 10 that are never primes in any smaller base b, 2<=b<10, expansions interpreted as decimal numbers.

Original entry on oeis.org

263, 269, 347, 397, 431, 461, 479, 499, 569, 599, 607, 677, 683, 719, 769, 797, 821, 929, 941, 1019, 1031, 1049, 1051, 1061, 1069, 1103, 1181, 1223, 1229, 1237, 1297, 1307, 1367, 1399, 1409, 1439, 1453, 1487, 1489, 1523, 1553, 1559, 1571, 1619, 1637
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Crossrefs

Programs

A052026 Composites base 10 that remain composite in all bases b, 2<=b<=10, expansions interpreted as decimal numbers.

Original entry on oeis.org

14, 18, 20, 24, 30, 32, 36, 40, 42, 44, 51, 54, 60, 62, 69, 70, 72, 74, 76, 78, 80, 86, 90, 92, 96, 98, 99, 100, 102, 104, 108, 110, 112, 114, 120, 124, 125, 126, 128, 129, 130, 132, 135, 140, 144, 146, 148, 150, 152, 156, 158, 159, 160, 162, 164, 168, 170, 174
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Crossrefs

Programs

  • Mathematica
    Select[Range@ 174, AllTrue[Table[FromDigits[IntegerDigits[#, i]], {i, 2, 10}], CompositeQ] &] (* Michael De Vlieger, Mar 24 2015, version 10 *)

A084482 Primes base 10 that remain primes in all nine bases b, 2<=b<=10, when the expansions are interpreted as decimal numbers.

Original entry on oeis.org

50006393431, 727533146383, 2250332130313, 2651541199513, 4437592255351, 4877749016143, 6777899690983, 7417899095713, 7431376081543, 7766799025303, 9078654198463, 10712216924641, 12244626455491, 13562282568103, 14180813918071, 14833027106593, 19479075240913, 19971686697103, 23196986067193, 34431442237963, 36429184518721, 49198998504223
Offset: 1

Views

Author

Jack Brennen, Jun 29 2003

Keywords

Comments

a(1) found by Jack Brennen on Jul 13 2001; remaining terms computed by Jack Brennen, Nov 15 2001.
The number must end with 1, 3, 7, or 9 in each base from 2 to 10; thus must be congruent to: 1 (mod 2), 1 (mod 3), 1 or 3 (mod 4), 1 or 3 (mod 5), 1 (mod 6), 1 or 3 (mod 7), 1 or 3 or 7 (mod 8), 1 or 7 (mod 9), 1 or 3 or 7 or 9 (mod 10).

Crossrefs

Programs

  • PARI
    isok(n) = sum(b=2, 10, isprime(subst(Pol(digits(n, b)), x, 10))) == 9; \\ Michel Marcus, Mar 22 2015

Extensions

Thanks to David W. Wilson for proposing the sequence and W. Edwin Clark for verifying the terms using Maple's command isprime.

A052027 Primes in base 10 that remain primes in seven bases b, 2<=b<=10, expansions interpreted as decimal numbers.

Original entry on oeis.org

5, 9241, 17791, 330289, 391231, 1005481, 1210483, 2378143, 2469241, 2779939, 2840041, 6817501, 8320831, 9865711, 10871407, 11087191, 12259603, 13645393, 15665833, 16707883, 17694463, 25751863, 27794287, 31488481
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Crossrefs

Programs

  • Mathematica
    Select[Prime[Range@ 100000], Count[PrimeQ /@ Table[FromDigits[IntegerDigits[#, i]], {i, 2, 10}], True] == 7 &] (* Michael De Vlieger, Mar 21 2015, after Harvey P. Dale at A052032 *)

Extensions

Missing terms 2378143 and 2469241 added by Sebastian Petzelberger, Mar 21 2015

A052032 Primes base 10 that remain prime in one (and only one) other base b, 2<=b<10, expansions interpreted as decimal numbers.

Original entry on oeis.org

41, 53, 73, 107, 113, 131, 137, 139, 167, 173, 223, 233, 239, 257, 271, 293, 317, 389, 401, 467, 491, 509, 521, 557, 593, 641, 661, 691, 701, 739, 761, 809, 827, 829, 839, 853, 859, 863, 881, 887, 911, 937, 971, 977, 991, 1013, 1063, 1109, 1129, 1151, 1153
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Crossrefs

Programs

  • Mathematica
    Select[Prime[Range[200]],Count[PrimeQ/@Table[FromDigits[ IntegerDigits[ #,i]],{i,2,9}],True]==1&] (* Harvey P. Dale, Oct 13 2012 *)

Extensions

Definition clarified by Harvey P. Dale, Oct 13 2012

A052028 Primes base 10 that remain primes in six bases b, 2<=b<=10, expansions interpreted as decimal numbers.

Original entry on oeis.org

157, 523, 1249, 1483, 1753, 4051, 9187, 10531, 22921, 25981, 29599, 35899, 51031, 57751, 67579, 79939, 98323, 103561, 110581, 148471, 150193, 150343, 249703, 259183, 277063, 278623, 331081, 335833, 353401, 391903, 424819, 435553, 504547
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Crossrefs

Programs

A256350 Composites in base 10 that remain composite in exactly eight bases b, 2 <= b <= 10, expansions interpreted as decimal numbers.

Original entry on oeis.org

4, 6, 12, 26, 27, 35, 38, 45, 46, 48, 49, 50, 52, 56, 57, 58, 63, 64, 65, 66, 68, 77, 81, 82, 84, 85, 88, 95, 105, 116, 117, 118, 119, 121, 122, 134, 136, 138, 142, 153, 154, 161, 165, 166, 171, 175, 176, 187, 188, 190, 192, 195, 207, 208, 218, 219, 220, 225
Offset: 1

Views

Author

Sebastian Petzelberger, Mar 25 2015

Keywords

Crossrefs

A256356 Composites in base 10 that remain composite in exactly two bases b, 2 <= b <= 10, expansions interpreted as decimal numbers.

Original entry on oeis.org

33247243, 64037779, 104865433, 130237003, 238561081, 550677781, 947051353, 1013991553, 1246382791, 1343122201, 1607697631, 1609062751, 1632753601, 1788658063, 2203645111, 2364166213, 2393866411, 2480419783, 2518589671, 2544177511, 2668538575, 3029334883
Offset: 1

Views

Author

Sebastian Petzelberger, Mar 25 2015

Keywords

Comments

Are there any remaining composites in only one other base?

Crossrefs

A052029 Primes base 10 that remain primes in five bases b, 2<=b<=10, expansions interpreted as decimal numbers.

Original entry on oeis.org

7, 43, 71, 163, 199, 283, 307, 367, 463, 571, 757, 1033, 1163, 1627, 1873, 2683, 3041, 3691, 3967, 4483, 4651, 4729, 4951, 4973, 5407, 6073, 6961, 7351, 7537, 8053, 8599, 9103, 9817, 10321, 10831, 11251, 11383, 11743, 12433, 12853, 13219, 14419, 14479
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Crossrefs

Programs

  • Mathematica
    Select[Prime[Range@ 1800], Count[PrimeQ /@ Table[FromDigits[IntegerDigits[#, i]], {i, 2, 10}], True] == 5 &] (* Michael De Vlieger, Mar 20 2015, after Harvey P. Dale at A052032 *)
  • PARI
    lista(nn, nb=5) = {forprime(p=2, nn, if (sum(b=2, 10, isprime(subst(Pol(digits(p, b)), x, 10))) == nb, print1(p, ", ")););} \\ Michel Marcus, Mar 21 2015

A052030 Primes base 10 that remain primes in four bases b, 2<=b<=10, expansions interpreted as decimal numbers.

Original entry on oeis.org

19, 23, 37, 67, 79, 103, 127, 191, 193, 211, 229, 277, 311, 313, 337, 379, 409, 433, 443, 577, 613, 619, 631, 643, 647, 653, 787, 857, 883, 907, 919, 947, 997, 1021, 1039, 1087, 1097, 1123, 1171, 1279, 1423, 1429, 1447, 1459, 1471, 1567, 1597, 1669, 1693
Offset: 1

Views

Author

Patrick De Geest, Dec 15 1999

Keywords

Examples

			19 is 103_4, 31_6, 23_8 and 19_10.
		

Crossrefs

Programs

Showing 1-10 of 17 results. Next