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 11 results. Next

A098417 A098414(n) - (A007529(n) + A098415(n))/2.

Original entry on oeis.org

-1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, 1, 1, -1, -1, 1, -1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, -1, 1, -1, 1, -1, 1, -1, 1, -1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, 1, -1, 1, -1, -1, 1, -1, -1, -1, 1, 1, -1, -1, 1, -1, -1, -1, 1, -1, 1, 1, -1
Offset: 1

Views

Author

Reinhard Zumkeller, Sep 07 2004

Keywords

Comments

(A007529(n),2*A098416(n)+a(n), A098415(n)) is a prime triple (p,q,r) with p

A007529 Prime triples: p; p+2 or p+4; p+6 all prime.

Original entry on oeis.org

5, 7, 11, 13, 17, 37, 41, 67, 97, 101, 103, 107, 191, 193, 223, 227, 277, 307, 311, 347, 457, 461, 613, 641, 821, 823, 853, 857, 877, 881, 1087, 1091, 1277, 1297, 1301, 1423, 1427, 1447, 1481, 1483, 1487, 1607, 1663, 1693, 1783, 1867, 1871, 1873, 1993, 1997
Offset: 1

Keywords

Comments

Or, prime(m) such that prime(m+2) = prime(m)+6. - Zak Seidov, May 07 2012

References

  • H. Riesel, "Prime numbers and computer methods for factorization", Progress in Mathematics, Vol. 57, Birkhauser, Boston, 1985, Chap. 4, see p. 65.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Magma
    [NthPrime(n): n in [1..310] | (NthPrime(n)+6) eq NthPrime(n+2)]; // Bruno Berselli, May 07 2012
    
  • Maple
    N:= 10000: # to get all terms <= N
    Primes:= select(isprime, [seq(2*i+1, i=1..floor((N+5)/2))]):locs:= select(t -> Primes[t+2]-Primes[t]=6, [$1..nops(Primes)-2]):
    Primes[locs]; # Robert Israel, Apr 30 2015
  • Mathematica
    ptrsQ[n_]:=PrimeQ[n+6]&&(PrimeQ[n+2]||PrimeQ[n+4])
    Select[Prime[Range[400]],ptrsQ]  (* Harvey P. Dale, Mar 08 2011 *)
  • PARI
    p=2;q=3;forprime(r=5,1e4,if(r-p==6,print1(p", "));p=q;q=r) \\ Charles R Greathouse IV, May 07 2012

Formula

a(n) = A098415(n) - 6. - Zak Seidov, Apr 30 2015

A073648 Middle members of prime triples {p, p+2, p+6}.

Original entry on oeis.org

7, 13, 19, 43, 103, 109, 193, 229, 313, 349, 463, 643, 823, 859, 883, 1093, 1279, 1303, 1429, 1483, 1489, 1609, 1873, 1999, 2083, 2239, 2269, 2659, 2689, 3253, 3463, 3529, 3673, 3919, 4003, 4129, 4519, 4639, 4789, 4933, 4969, 5233, 5479, 5503, 5653, 6199
Offset: 1

Author

Amarnath Murthy, Aug 09 2002

Keywords

Crossrefs

Programs

  • Mathematica
    Transpose[Select[Partition[Prime[Range[850]],3,1],Differences[#]=={2,4}&]][[2]]  (* Harvey P. Dale, Feb 20 2011 *)

Formula

a(n) = A022004(n) + 2.

Extensions

More terms from Benoit Cloitre, Aug 13 2002

A098415 Greatest members r of prime triples (p,q,r) with p

Original entry on oeis.org

11, 13, 17, 19, 23, 43, 47, 73, 103, 107, 109, 113, 197, 199, 229, 233, 283, 313, 317, 353, 463, 467, 619, 647, 827, 829, 859, 863, 883, 887, 1093, 1097, 1283, 1303, 1307, 1429, 1433, 1453, 1487, 1489, 1493, 1613, 1669, 1699, 1789, 1873, 1877, 1879, 1999
Offset: 1

Author

Reinhard Zumkeller, Sep 07 2004

Keywords

Comments

Union of A098412 and A098413;
a(n)=A007529(n)+6; either a(n)=A098414(n)+2 or a(n)=A098414(n)+4.

Crossrefs

Programs

  • Mathematica
    Transpose[Select[Partition[Prime[Range[350]],3,1],#[[3]]- #[[1]] == 6&]][[3]] (* Harvey P. Dale, Mar 17 2015 *)
  • PARI
    is(n)=isprime(n) && isprime(n-6) && (isprime(n-2) || isprime(n-4)) \\ Charles R Greathouse IV, Feb 23 2017

A073649 Define the composite field of a prime q to be f(q) = (t,s) if p, q, r are three consecutive primes and q-p = t and r-q = s. This is a sequence of primes q with field (4,2).

Original entry on oeis.org

11, 17, 41, 71, 101, 107, 197, 227, 281, 311, 461, 617, 827, 857, 881, 1091, 1301, 1427, 1451, 1487, 1667, 1697, 1787, 1871, 1877, 1997, 2087, 2141, 2381, 2687, 2711, 2801, 3167, 3257, 3461, 3467, 3851, 4157, 4517, 4787, 5231, 5417, 5441, 5651, 5657
Offset: 1

Author

Amarnath Murthy, Aug 09 2002

Keywords

Crossrefs

Equals A022005 + 4.

Programs

  • Mathematica
    Transpose[Select[Partition[Prime[Range[1200]],3,1],Differences[#] == {4,2}&]] [[2]] (* Harvey P. Dale, Jul 23 2011 *)

Extensions

Corrected and extended by Benoit Cloitre, Aug 13 2002

A098420 Members of prime triples (p,q,r) with p < q < r = p + 6.

Original entry on oeis.org

5, 7, 11, 13, 17, 19, 23, 37, 41, 43, 47, 67, 71, 73, 97, 101, 103, 107, 109, 113, 191, 193, 197, 199, 223, 227, 229, 233, 277, 281, 283, 307, 311, 313, 317, 347, 349, 353, 457, 461, 463, 467, 613, 617, 619, 641, 643, 647, 821, 823, 827, 829, 853, 857, 859, 863
Offset: 1

Author

Reinhard Zumkeller, Sep 07 2004

Keywords

Comments

A098418(a(n)) > 0; complement of A098419 in A000040.
Union of A007529, A098414 and A098415.

Programs

  • Mathematica
    lst={};Do[p=Prime[n];If[PrimeQ[p2=p+2]&&PrimeQ[p6=p+6], AppendTo[lst, p];AppendTo[lst, p2];AppendTo[lst, p6]];If[PrimeQ[p4=p+4]&&PrimeQ[p6=p+6], AppendTo[lst, p];AppendTo[lst, p4];AppendTo[lst, p6]], {n, 6!}];Union[lst] (* Vladimir Joseph Stephan Orlovsky, Sep 25 2008 *)

A098418 Number of prime triples (p,q,r) with p

Original entry on oeis.org

0, 0, 1, 2, 3, 3, 3, 2, 1, 0, 0, 1, 2, 2, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 2, 3, 3, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 2, 1, 0, 1, 2, 2, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 2, 2, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1

Author

Reinhard Zumkeller, Sep 07 2004

Keywords

Comments

0 <= a(n) <= 3;
a(A098419(n))=0; a(A098420(n))>0; a(A098421(n))=1; a(A098422(n))=2; a(A098423(n))=3.

Examples

			A000040(13)=41: A007529(7)=41, A098414(6)=41 and
A098415(k)<>41 for all k, therefore a(13)=2.
		

Crossrefs

A098424 Number of prime triples (p,q,r) <= n with p

Original entry on oeis.org

0, 0, 0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 11
Offset: 1

Author

Reinhard Zumkeller, Sep 07 2004

Keywords

Comments

Convention: a prime triple is <= n iff its smallest member is <= n;
a(n) <= A098428(n).

Examples

			a(15) = #{(5,7,11),(7,11,13),(11,13,17),(13,17,19)} = 4.
		

Crossrefs

Programs

  • Haskell
    a098424 n = length [(p,q,r) | p <- takeWhile (<= n) a000040_list,
                let r = p + 6, a010051 r == 1, q <- [p+1..r-1], a010051 q == 1]
    -- Reinhard Zumkeller, Nov 15 2011
  • Mathematica
    With[{pts=Select[Partition[Prime[Range[1200]],3,1],Last[#]-First[#] == 6&]}, Table[Count[pts,?(First[#]<=n&)],{n,110}]] (* _Harvey P. Dale, Nov 09 2011 *)

A098423 Primes occurring in exactly three prime triples (p,q,r) with p

Original entry on oeis.org

11, 13, 17, 103, 107, 1487, 1873, 3463, 5653, 15733, 16063, 16067, 19423, 19427, 21017, 22277, 43783, 43787, 55337, 79693, 88813, 101113, 144167, 165707, 166847, 195737, 201827, 225347, 247607, 257863, 266683, 268817, 276043, 284743
Offset: 1

Author

Reinhard Zumkeller, Sep 07 2004

Keywords

Comments

A098418(a(n)) = 3; subsequence of A098420.
This sequence consists of all integers of the form (prime(m)*prime(m+4)+36)/prime(m+2), for m>0, where prime(m) = A000040(m). Also note that the integers resulting from that rule equal prime(m+2), therefore a(n) also consists of all integers of the form sqrt[prime(m)*prime(m+4)+36]. - Richard R. Forberg, Jan 11 2016

Examples

			A000040(27)=103: A007529(11)=103, A098414(10)=103 and A098415(9)=103, therefore 103 is a term.
		

Crossrefs

A166007 Number of ones in the binary representation of the middle member q of the prime triple (p,q,r) with p

Original entry on oeis.org

3, 3, 3, 2, 3, 3, 4, 4, 4, 5, 5, 5, 3, 4, 5, 5, 4, 6, 5, 6, 6, 7, 5, 4, 7, 7, 6, 7, 6, 7, 4, 4, 9, 5, 6, 6, 6, 7, 7, 8, 6, 5, 5, 5, 9, 8, 6, 7, 8, 9, 4, 5, 6, 8, 7, 6, 6, 9, 4, 7, 7, 8, 7, 7, 6, 7, 7, 7, 7, 7, 9, 8, 3, 6, 6, 7, 7, 7, 7, 6, 7, 8, 6, 6, 5, 8
Offset: 1

Author

Steven Lubars (lubars(AT)gmail.com), Oct 03 2009

Keywords

Examples

			For n = 3, (p, q, r) = (11, 13, 17), q = 13
Decimal 13 = Binary 1101
a(3) = Number of ones in 1101 = 3
		

Crossrefs

Programs

  • Mathematica
    DigitCount[#,2,1]&/@Transpose[Select[Partition[Prime[Range[1000]],3,1], Last[#]-First[#]==6&]][[2]] (* Harvey P. Dale, Dec 03 2014 *)

Extensions

More terms from Harvey P. Dale, Dec 03 2014
Showing 1-10 of 11 results. Next