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.

A247871 Least prime factor of A247679.

Original entry on oeis.org

5, 5, 11, 7, 5, 7, 5, 17, 11, 13, 5, 7, 5, 7, 5, 13, 17, 5, 11, 5, 7, 5, 29, 7, 5, 23, 19, 5, 7, 13, 5, 11, 7, 5, 17, 5, 13, 11, 19, 5, 23, 7, 31, 5, 11, 7, 5, 5, 7, 19, 11, 5, 41, 13, 7, 23, 5, 17, 5, 29, 37, 5, 19, 7, 5, 11, 17, 7, 5, 23, 13, 5, 7, 11, 5, 7, 5, 13, 41, 11, 43, 5, 31, 37, 5, 7, 11, 5, 17, 7, 5, 5, 7, 13, 29, 5
Offset: 1

Views

Author

Odimar Fabeny, Sep 25 2014

Keywords

Links

Crossrefs

Cf. A056608, A247679.

Programs

  • Mathematica
    FactorInteger[#][[1,1]]&/@Select[Range[17,4000,18],CompositeQ] (* Harvey P. Dale, Jun 19 2022 *)

A247899 First differences of A247679.

Original entry on oeis.org

90, 18, 18, 54, 72, 18, 18, 18, 36, 18, 18, 72, 54, 36, 36, 18, 36, 72, 18, 36, 54, 54, 18, 18, 54, 18, 18, 18, 36, 36, 18, 36, 36, 36, 54, 18, 18, 18, 36, 18, 18, 36, 18, 54, 18, 18, 90, 18, 18, 36, 18, 18, 18, 18, 18, 18, 18, 72, 18, 18, 54, 18, 18, 54, 18, 36, 18, 18, 36, 18, 36, 18, 18, 54, 54, 36, 18, 18, 18, 18, 18
Offset: 1

Views

Author

Odimar Fabeny, Sep 26 2014

Keywords

Comments

All terms have digital root equal to 9.

Links

Crossrefs

Cf. A247679.

A247676 Odd composite numbers congruent to 2 modulo 9.

Original entry on oeis.org

65, 119, 155, 209, 245, 299, 335, 371, 407, 425, 497, 515, 533, 551, 605, 623, 695, 713, 731, 749, 767, 785, 803, 875, 893, 965, 1001, 1037, 1055, 1073, 1127, 1145, 1199, 1235, 1253, 1271, 1325, 1343, 1379, 1397, 1415, 1469, 1505, 1541, 1577, 1595, 1631, 1649
Offset: 1

Views

Author

Odimar Fabeny, Sep 22 2014

Keywords

Comments

Subsequence of A017185 (9n+2).
Composites == 11 mod 18. - Robert Israel, Sep 24 2014

Links

Crossrefs

Cf. A017185, A247678, A247679, A247681, A247682, A247683.

Programs

  • Maple
    remove(isprime,[seq(18*k+11,k=1..1000)]); # Robert Israel, Sep 24 2014
  • Mathematica
    Select[18Range[100] + 11, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 25 2014 *)
Select[Range[11,2000,18],CompositeQ] (* Harvey P. Dale, Oct 29 2023 *)
  • PARI
    lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 2), print1(n, ", ")););} \\ Michel Marcus, Sep 22 2014

A247678 Odd composite numbers congruent to 4 modulo 9.

Original entry on oeis.org

49, 85, 121, 175, 247, 265, 301, 319, 355, 391, 427, 445, 481, 517, 535, 553, 589, 625, 679, 697, 715, 805, 841, 895, 913, 931, 949, 985, 1003, 1057, 1075, 1111, 1147, 1165, 1183, 1219, 1255, 1273, 1309, 1345, 1363, 1417, 1435, 1507, 1525, 1561, 1615, 1633
Offset: 1

Views

Author

Odimar Fabeny, Sep 22 2014

Keywords

Links

Crossrefs

Cf. A017209 (9n + 4, supersequence of this sequence), A247676, A247679, A247681, A247682, A247683.

Programs

  • Mathematica
    Select[18Range[125] + 13, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 24 2014 *)
Select[Range[13,1700,18],CompositeQ] (* Harvey P. Dale, Aug 21 2024 *)
  • PARI
    lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 4), print1(n, ", ")); ); } \\ Michel Marcus, Sep 22 2014

A247681 Odd nonprimes congruent to 1 modulo 9.

Original entry on oeis.org

1, 55, 91, 145, 217, 235, 253, 289, 325, 343, 361, 415, 451, 469, 505, 559, 595, 649, 667, 685, 703, 721, 775, 793, 847, 865, 901, 955, 973, 1027, 1045, 1081, 1099, 1135, 1189, 1207, 1225, 1243, 1261, 1315, 1333, 1351, 1369, 1387, 1405
Offset: 1

Views

Author

Odimar Fabeny, Sep 22 2014

Keywords

Comments

Subsequence of A017173.

Links

Crossrefs

Cf. A017173, A247676, A247678, A247679, A247682, A247683, A247900 (first differences).

Programs

  • Mathematica
    Select[18Range[0, 99] + 1, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 25 2014 *)
Select[Range[1,1500,18],!PrimeQ[#]&] (* Harvey P. Dale, Mar 07 2018 *)
  • PARI
    lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 1), print1(n, ", ")); ); } \\ Michel Marcus, Sep 22 2014

A247682 Odd composite numbers congruent to 5 modulo 9.

Original entry on oeis.org

77, 95, 185, 203, 221, 275, 329, 365, 437, 455, 473, 527, 545, 581, 635, 671, 689, 707, 725, 779, 815, 833, 851, 869, 905, 923, 959, 995, 1067, 1085, 1121, 1139, 1157, 1175, 1211, 1247, 1265, 1337, 1355, 1391, 1445, 1463, 1517, 1535, 1589
Offset: 1

Views

Author

Odimar Fabeny, Sep 22 2014

Keywords

Comments

Subsequence of A017221 (9n + 5).

Links

Crossrefs

Cf. A017221, A247676, A247678, A247679, A247681, A247683.

Programs

  • Mathematica
    Select[18Range[100] + 5, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 25 2014 *)
Select[Range[5,2000,18],CompositeQ] (* Harvey P. Dale, Feb 21 2016 *)
  • PARI
    lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 5), print1(n, ", ")); ); } \\ Michel Marcus, Sep 22 2014

A247683 Odd composite numbers congruent to 7 modulo 9.

Original entry on oeis.org

25, 115, 133, 169, 187, 205, 259, 295, 385, 403, 475, 493, 511, 529, 565, 583, 637, 655, 745, 763, 781, 799, 817, 835, 871, 889, 925, 943, 961, 979, 1015, 1105, 1141, 1159, 1177, 1195, 1267, 1285, 1339, 1357, 1375, 1393, 1411, 1465, 1501
Offset: 1

Views

Author

Odimar Fabeny, Sep 22 2014

Keywords

Comments

Subsequence of A017245 (9n + 7).

Links

Crossrefs

Cf. A017245, A247676, A247678, A247679, A247681, A247682.

Programs

  • Mathematica
    Select[18Range[100] + 7, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 25 2014 *)
Select[Range[1,1501,2],CompositeQ[#]&&Mod[#,9]==7&] (* or *) Select[Range[7,1501,18],CompositeQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 31 2021 *)
  • PARI
    lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 7), print1(n, ", ")); ); } \\ Michel Marcus, Sep 22 2014
Showing 1-7 of 7 results.

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