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 1-5 of 5 results.

A060229 Smaller member of a twin prime pair whose mean is a multiple of A002110(3)=30.

Original entry on oeis.org

29, 59, 149, 179, 239, 269, 419, 569, 599, 659, 809, 1019, 1049, 1229, 1289, 1319, 1619, 1949, 2129, 2309, 2339, 2549, 2729, 2789, 2969, 2999, 3119, 3299, 3329, 3359, 3389, 3539, 3929, 4019, 4049, 4229, 4259, 4649, 4799, 5009, 5099, 5279, 5519, 5639
Offset: 1

Views

Author

Labos Elemer, Mar 21 2001

Keywords

Comments

Equivalently, smaller of twin prime pair with primes in different decades.
Primes p such that p and p+2 are prime factors of Fibonacci(p-1) and Fibonacci(p+1) respectively. - Michel Lagneau, Jul 13 2016
The union of this sequence and A282326 gives A132243. - Martin Renner, Feb 11 2017
The union of {3,5}, A282321, A282323 and this sequence gives A001359. - Martin Renner, Feb 11 2017
The union of {3,5,7}, A282321, A282322, A282323, A282324, this sequence and A282326 gives A001097. - Martin Renner, Feb 11 2017
Number of terms less than 10^k, k=2,3,4,...: 2, 11, 72, 407, 2697, 19507, 146516, ... - Muniru A Asiru, Jan 29 2018

Examples

			For the pair {149,151} (149 + 151)/2 = 5*30.
		

Crossrefs

Programs

  • GAP
    Filtered(List([0..200], k -> 30*k-1), n -> IsPrime(n) and IsPrime(n+2));  # Muniru A Asiru, Feb 02 2018
  • Magma
    [p: p in PrimesUpTo(7000) | IsPrime(p+2) and p mod 30 eq 29 ]; // Vincenzo Librandi, Feb 13 2017
    
  • Maple
    isA060229 := proc(n)
        if modp(n+1,30) =0 and isprime(n) and isprime(n+2) then
            true;
        else
            false;
        end if;
    end proc:
    A060229 := proc(n)
        option remember;
        if n =1 then
            29;
        else
            for a from procname(n-1)+2 by 2 do
                if isA060229(a) then
                    return a;
                end if;
            end do:
        end if;
    end proc:
    seq(A060229(n),n=1..80) ; # R. J. Mathar, Feb 19 2017
  • Mathematica
    Select[Prime@ Range[10^3], PrimeQ[# + 2] && Mod[# + 1, 30] == 0 &] (* Michael De Vlieger, Jul 14 2016 *)
  • PARI
    isok(n) = isprime(n) && isprime(n+2) && !((n+1) % 30); \\ Michel Marcus, Dec 11 2013
    

Extensions

Minor edits by Ray Chandler, Apr 02 2009

A282326 Greater of twin primes congruent to 1 (mod 30).

Original entry on oeis.org

31, 61, 151, 181, 241, 271, 421, 571, 601, 661, 811, 1021, 1051, 1231, 1291, 1321, 1621, 1951, 2131, 2311, 2341, 2551, 2731, 2791, 2971, 3001, 3121, 3301, 3331, 3361, 3391, 3541, 3931, 4021, 4051, 4231, 4261, 4651, 4801, 5011, 5101, 5281, 5521, 5641, 5851
Offset: 1

Views

Author

Martin Renner, Feb 11 2017

Keywords

Comments

The union of [A060229 and this sequence] is A132243.
The union of [{5, 7}, A282322, A282324 and this sequence] is the greater of twin primes sequence A006512.
The union of [{3, 5, 7}, A282321 to A060229 and this sequence] is the twin primes sequence A001097.
Number of terms less than 10^k, k=2,3,4,...: 2, 11, 72, 407, 2697, 19507, 146516, ... - Muniru A Asiru, Mar 05 2018

Crossrefs

Programs

  • GAP
    Filtered(List([0..300], k -> 30*k+1), n -> IsPrime(n-2) and IsPrime(n));  # Muniru A Asiru, Mar 05 2018
  • Maple
    select(n -> isprime(n-2) and isprime(n), [seq(30*k+1, k=0..300)]); # Muniru A Asiru, Mar 05 2018
  • Mathematica
    1 + Select[30 Range@ 200, AllTrue[# + {-1, 1}, PrimeQ] &] (* Michael De Vlieger, Mar 26 2018 *)
  • PARI
    list(lim)=my(v=List(),p=2); forprime(q=3,lim, if(q-p==2 && q%30==1, listput(v,q)); p=q); Vec(v) \\ Charles R Greathouse IV, Feb 14 2017
    

A132242 Twin primes congruent to {17, 19} mod 30.

Original entry on oeis.org

17, 19, 107, 109, 137, 139, 197, 199, 227, 229, 347, 349, 617, 619, 827, 829, 857, 859, 1277, 1279, 1427, 1429, 1487, 1489, 1607, 1609, 1667, 1669, 1697, 1699, 1787, 1789, 1877, 1879, 1997, 1999, 2027, 2029, 2087, 2089, 2237, 2239, 2267, 2269, 2657, 2659
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Crossrefs

Programs

  • Mathematica
    a[0] = 7; a[n_] := a[n] = a[n - 1] + 10; Flatten[Table[If[PrimeQ[a[n]] && PrimeQ[a[n] + 2], {a[n],a[n] + 2}, {}], {n, 0, 1000}]] (* Roger L. Bagula, May 04 2008 *)

Extensions

More terms from Roger L. Bagula, May 04 2008

A076746 List giving pairs of primes of the form 10k+3 and 10k+7.

Original entry on oeis.org

3, 7, 13, 17, 43, 47, 103, 107, 163, 167, 193, 197, 223, 227, 313, 317, 463, 467, 613, 617, 643, 647, 673, 677, 823, 827, 853, 857, 883, 887, 1093, 1097, 1213, 1217, 1303, 1307, 1423, 1427, 1483, 1487, 1663, 1667, 1693, 1697, 1783, 1787, 1873, 1877, 1993
Offset: 1

Views

Author

Cino Hilliard, Nov 11 2002

Keywords

Comments

Except for 3 and 7, all pairs are 30k+13 and 30k+17.
Is this sequence infinite?

Examples

			43 and 47 are in the sequence because both are prime; 73 and 77 aren't because not both are primes.
		

Crossrefs

Programs

  • Magma
    &cat[[10*k+3, 10*k+7]: k in [0..250]| IsPrime(10*k+3) and IsPrime(10*k+7)]; // Vincenzo Librandi, Jun 17 2016
  • Mathematica
    a[0] = 3; a[n_] := a[n] = a[n - 1] + 10; Flatten[Table[If[PrimeQ[a[n]] && PrimeQ[a[n] + 4], {a[n],a[n] + 4}, {}], {n, 0, 1000}]] (* Roger L. Bagula, May 04 2008 *)
    Flatten[Select[Table[10n+{3,7},{n,0,200}],And@@PrimeQ[#]&]] (* Harvey P. Dale, Dec 31 2013 *)
  • PARI
    forstep(x=3,2000,10, if(isprime(x) && isprime(x+4), print1(x, ", ", x+4, ", ")))
    

Extensions

Edited by Don Reble, Jun 07 2003
More terms from Roger L. Bagula, May 04 2008

A138122 Cousin primes, the lower of which is 7 (mod 10).

Original entry on oeis.org

7, 11, 37, 41, 67, 71, 97, 101, 127, 131, 277, 281, 307, 311, 397, 401, 457, 461, 487, 491, 757, 761, 877, 881, 907, 911, 937, 941, 967, 971, 1087, 1091, 1297, 1301, 1447, 1451, 1567, 1571, 1597, 1601, 1867, 1871, 2137, 2141, 2347, 2351, 2377, 2381, 2437
Offset: 1

Views

Author

Roger L. Bagula, May 04 2008

Keywords

Comments

Start from the intersection of A023200 and A030432, then add the associated members of A046132. The last digits are obviously periodic as A010688. - R. J. Mathar, Nov 26 2008

Crossrefs

Programs

  • Mathematica
    a[0] = 7; a[n_] := a[n] = a[n - 1] + 10; Flatten[Table[If[PrimeQ[a[n]] && PrimeQ[a[n] + 4], {a[n],a[n] + 4}, {}], {n, 0, 1000}]]

Extensions

Replaced Mathematica definition by humanly readable phrase. - R. J. Mathar, Nov 26 2008
Showing 1-5 of 5 results.