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.

Previous Showing 11-14 of 14 results.

A004621 Divisible only by primes congruent to 3 mod 7.

Original entry on oeis.org

1, 3, 9, 17, 27, 31, 51, 59, 73, 81, 93, 101, 153, 157, 177, 199, 219, 227, 241, 243, 269, 279, 283, 289, 303, 311, 353, 367, 409, 459, 471, 479, 521, 527, 531, 563, 577, 597, 619, 647, 657, 661, 681, 723, 729, 773, 787, 807, 829, 837, 849, 857, 867, 909, 933
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

Links

Crossrefs

Cf. A045437 (divisors).

Programs

  • Magma
    [n: n in [1..1000] | forall{d: d in PrimeDivisors(n) | d mod 7 eq 3}]; // Vincenzo Librandi, Aug 20 2012
  • Mathematica
    ok[1]=True;ok[n_]:=And@@(Mod[#,7]==3&)/@FactorInteger[n][[All,1]];Select[Range[3000],ok] (* Vincenzo Librandi, Aug 20 2012 *)

Extensions

Offset changed from 0 to 1 by Vincenzo Librandi, Aug 20 2012

A140442 Primes congruent to 9 mod 14.

Original entry on oeis.org

23, 37, 79, 107, 149, 163, 191, 233, 317, 331, 359, 373, 401, 443, 457, 499, 541, 569, 653, 709, 751, 821, 863, 877, 919, 947, 1031, 1087, 1129, 1171, 1213, 1283, 1297, 1367, 1381, 1409, 1423, 1451, 1493, 1549, 1619, 1759, 1787, 1801, 1871, 1913, 1997
Offset: 1

Views

Author

Juri-Stepan Gerasimov, Jun 26 2008

Keywords

Links

Crossrefs

Primes arising in sequences A045437, A045458, A045471, A045473.
A090613 gives prime index.
Cf. A090614.

Programs

Formula

a(n) = A045392(n+1) = A045383(n+2). - Zak Seidov, Mar 12 2014
a(n) ~ 6n log n. - Charles R Greathouse IV, Jul 03 2016

Extensions

1451 inserted by R. J. Mathar, Sep 13 2008

A154611 Numbers n such that 7*n+3 is not prime.

Original entry on oeis.org

1, 3, 5, 6, 7, 9, 11, 12, 13, 15, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 29, 30, 31, 33, 35, 36, 37, 39, 41, 42, 43, 45, 46, 47, 48, 49, 51, 53, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 66, 67, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79
Offset: 1

Views

Author

Vincenzo Librandi, Jan 15 2009

Keywords

Comments

The even terms are the integer values of (4*h*k + 2*k + 2*h - 2)/7, where h and k are positive integers. - Vincenzo Librandi, Jan 17 2013
The corresponding composite numbers are 10, 24, 38, 45, 52, 66, 80, 87, 94, 108, 115, 122, 129, ... - Michael B. Porter, Jan 17 2013

Links

Crossrefs

Cf. A089033, A045437, A017017.

Programs

  • Magma
    [n: n in [0..80] | not IsPrime(7*n+3)]; // Vincenzo Librandi, Apr 05 2013
  • Mathematica
    With[{nn=100},Sort[Join[Range[1,nn-1,2],Select[Range[0,nn,2], !PrimeQ[ 7#+3]&]]]] (* Harvey P. Dale, Aug 22 2012 *)
Select[Range[0, 100], !PrimeQ[7 # + 3]&] (* Vincenzo Librandi, Apr 05 2013 *)

Extensions

Erroneous comments deleted by N. J. A. Sloane, Jun 23 2010

A140380 Composites of the form 14k + 3.

Original entry on oeis.org

45, 87, 115, 129, 143, 171, 185, 213, 255, 297, 325, 339, 381, 395, 423, 437, 451, 465, 493, 507, 535, 549, 591, 605, 633, 675, 689, 703, 717, 731, 745, 759, 801, 815, 843, 871, 885, 899, 913, 927, 955, 969, 1011, 1025, 1053, 1067, 1081, 1095, 1137, 1165
Offset: 1

Views

Author

Juri-Stepan Gerasimov, Jun 13 2008

Keywords

Crossrefs

Cf. A045437.

Programs

  • Magma
    [(14*n+3): n in [0..100]|not IsPrime(14*n+3)] // Vincenzo Librandi, Dec 18 2010
  • Mathematica
    Select[14Range[100]+3,!PrimeQ[#]&] (* Harvey P. Dale, Aug 15 2011 *)

Extensions

Edited by R. J. Mathar, Jun 16 2008
Previous Showing 11-14 of 14 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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