A247681 -id:A247681 - cp's OEIS frontend

A247900 First differences of A247681.

54, 36, 54, 72, 18, 18, 36, 36, 18, 18, 54, 36, 18, 36, 54, 36, 54, 18, 18, 18, 18, 54, 18, 54, 18, 36, 54, 18, 54, 18, 36, 18, 36, 54, 18, 18, 18, 18, 54, 18, 18, 18, 18, 18, 36, 36, 18, 18, 72, 18, 36, 36, 36, 18, 36, 54, 18, 18, 36, 18, 18, 18, 18, 18, 54, 36, 36, 18, 72, 18, 18, 72, 18, 36, 36, 18, 18, 18, 36, 90

Offset: 1

Odimar Fabeny, Sep 26 2014

All terms have digital root equal to 9.

Odimar Fabeny, Table of n, a(n) for n = 1..9999 [first term removed by _Georg Fischer_, Sep 02 2020]

Cf. A247681.

Differences[Select[Range[1,3500,18],!PrimeQ[#]&]] (* Harvey P. Dale, Apr 25 2018 *)

First term 54 removed by Georg Fischer, Sep 02 2020

A247872 Least prime factor of A247681(n).

Original entry on oeis.org

5, 7, 5, 7, 5, 11, 17, 5, 7, 19, 5, 11, 7, 5, 13, 5, 11, 23, 5, 19, 7, 5, 13, 7, 5, 17, 5, 7, 13, 5, 23, 7, 5, 29, 17, 5, 11, 13, 5, 31, 7, 37, 19, 5, 11, 7, 5, 17, 5, 7, 11, 5, 29, 7, 5, 17, 11, 5, 31, 23, 41, 5, 13, 7, 5, 19, 7, 5, 13, 5, 7, 5, 23, 7, 5, 19, 11, 31, 5, 5, 7, 11, 5, 37, 7, 5, 47, 53, 11, 5, 7, 43, 13, 5, 7

Offset: 2

Odimar Fabeny, Sep 25 2014

Odimar Fabeny, Table of n, a(n) for n = 2..10000

Cf. A056608, A247681.

count:= 0:
for n from 1 while count < 100 do
   m:= 1+18*n;
   if not isprime(m) then
      count:= count+1;
      A[count]:= min(numtheory:-factorset(m))
   fi
od:
seq(A[i],i=1..count); # Robert Israel, Sep 30 2014

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

Odimar Fabeny, Sep 22 2014

Subsequence of A017185 (9n+2).

Composites == 11 mod 18. - Robert Israel, Sep 24 2014

Odimar Fabeny, Table of n, a(n) for n = 1..10000

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

remove(isprime,[seq(18*k+11,k=1..1000)]); # Robert Israel, Sep 24 2014

Select[18Range[100] + 11, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 25 2014 *)
Select[Range[11,2000,18],CompositeQ] (* Harvey P. Dale, Oct 29 2023 *)

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

Odimar Fabeny, Sep 22 2014

Odimar Fabeny, Table of n, a(n) for n = 1..10000

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

Select[18Range[125] + 13, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 24 2014 *)
Select[Range[13,1700,18],CompositeQ] (* Harvey P. Dale, Aug 21 2024 *)

lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 4), print1(n, ", ")); ); } \\ Michel Marcus, Sep 22 2014

A247679 Composite numbers congruent to 17 modulo 18.

Original entry on oeis.org

35, 125, 143, 161, 215, 287, 305, 323, 341, 377, 395, 413, 485, 539, 575, 611, 629, 665, 737, 755, 791, 845, 899, 917, 935, 989, 1007, 1025, 1043, 1079, 1115, 1133, 1169, 1205, 1241, 1295, 1313, 1331, 1349, 1385, 1403, 1421, 1457, 1475

Offset: 1

Odimar Fabeny, Sep 22 2014

Subsequence of A017257 (9n + 8).

Odimar Fabeny, Table of n, a(n) for n = 1..10000

Cf. A017257, A247676, A247678, A247681, A247682, A247683.

Select[18Range[100] - 1, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 25 2014 *)
Select[Range[17,1500,18],CompositeQ] (* Harvey P. Dale, Jun 19 2022 *)

lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 8), print1(n, ", ")); ); } \\ Michel Marcus, Sep 22 2014

a(n) ~ 18n. - Charles R Greathouse IV, Sep 27 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

Odimar Fabeny, Sep 22 2014

Subsequence of A017221 (9n + 5).

Odimar Fabeny, Table of n, a(n) for n = 1..10000

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

Select[18Range[100] + 5, Not[PrimeQ[#]] &] (* Alonso del Arte, Sep 25 2014 *)
Select[Range[5,2000,18],CompositeQ] (* Harvey P. Dale, Feb 21 2016 *)

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

Odimar Fabeny, Sep 22 2014

Subsequence of A017245 (9n + 7).

Odimar Fabeny, Table of n, a(n) for n = 1..10000

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

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 *)

lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 7), print1(n, ", ")); ); } \\ Michel Marcus, Sep 22 2014

cp's OEIS Frontend

A247900 First differences of A247681.

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A247872 Least prime factor of A247681(n).

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Maple

A247676 Odd composite numbers congruent to 2 modulo 9.

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A247678 Odd composite numbers congruent to 4 modulo 9.

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A247679 Composite numbers congruent to 17 modulo 18.

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A247682 Odd composite numbers congruent to 5 modulo 9.

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A247683 Odd composite numbers congruent to 7 modulo 9.

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