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 1-4 of 4 results.

A039949 Primes of the form 30n - 13.

Original entry on oeis.org

17, 47, 107, 137, 167, 197, 227, 257, 317, 347, 467, 557, 587, 617, 647, 677, 797, 827, 857, 887, 947, 977, 1097, 1187, 1217, 1277, 1307, 1367, 1427, 1487, 1607, 1637, 1667, 1697, 1787, 1847, 1877, 1907, 1997, 2027, 2087, 2207, 2237, 2267, 2297, 2357, 2417
Offset: 1

Views

Author

Keywords

Comments

This linear form produces the most primes for n between 1 and 1000 (411/1000).
Primes congruent to 17 (mod 30). - Omar E. Pol, Aug 15 2007
Primes ending in 7 with (SOD-1)/3 non-integer where SOD is sum of digits. - Ki Punches
Or primes p such that (p mod 3) = (p mod 5) and (p mod 2) <> (p mod 3), (p > 2). - Mikk Heidemaa, Jan 19 2016

References

  • C. Clawson, Mathematical Mysteries, Plenum Press, 1996, p. 173

Crossrefs

Programs

Formula

a(n) = A158648(n)*30 + 17. - Ray Chandler, Apr 07 2009
Intersection of A030432 and A007528. - Ray Chandler, Apr 07 2009
a(n) = A141860(n+1). - Zak Seidov, Apr 15 2015

Extensions

Extended by Ray Chandler, Apr 07 2009

A267540 Primes p such that p (mod 3) = p (mod 5).

Original entry on oeis.org

2, 17, 31, 47, 61, 107, 137, 151, 167, 181, 197, 211, 227, 241, 257, 271, 317, 331, 347, 421, 467, 541, 557, 571, 587, 601, 617, 631, 647, 661, 677, 691, 751, 797, 811, 827, 857, 887, 947, 977, 991, 1021, 1051, 1097, 1171, 1187, 1201, 1217, 1231, 1277, 1291
Offset: 1

Views

Author

Mikk Heidemaa, Jan 16 2016

Keywords

Comments

Or primes p such that p (mod 15) = {1, 2}.
Terminal digits in a(7)...a(32) alternate 26 times (7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1). 25 differences between the 2 consecutive terms in this range show patterns as well.
A differenceroot function can generate the terms a(7)...a(32).

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(2000) | p mod 3 eq p mod 5]; // Vincenzo Librandi, Jan 17 2016
    
  • Maple
    select(isprime, [seq(seq(15*i+j, j= 1..2), i=0..10000)]); # Robert Israel, Jan 17 2016
  • Mathematica
    Select[ Prime[ Range[10000]], (Mod[#,3] == Mod[#,5]) &] (* Or *)
    Select[ Prime[ Range[10000]], 0 < Mod[#,15] < 3 &]
  • PARI
    lista(nn) = forprime(p=2, nn, if(p%3 == p%5, print1(p, ", "))); \\ Altug Alkan, Jan 17 2016

Formula

a(n) = 1/2*((-1)^n*(3*(-1)^n*(10n+81)-1)) with (1
G.f.: (x*(-14x^6-32x^5+16x^4+30x^3-x+14)+17)/((x-1)^2*(x+1)) generates a(2)...a(16), (0<=x<15).
G.f.: (x*(x*(30x*(-2x^4-x^3+x+2)-301)+14)+317)/((x-1)^2*(x+1)) generates a(17)...a(32), (0<=x<16).

Extensions

More terms from Vincenzo Librandi, Jan 17 2016

A220081 Primes of the form 15*k^2 - 15*k + 17.

Original entry on oeis.org

17, 47, 107, 197, 317, 467, 647, 857, 1097, 1367, 1667, 1997, 2357, 3167, 3617, 5147, 5717, 6317, 6947, 7607, 8297, 9767, 12197, 13967, 14897, 18917, 19997, 21107, 22247, 23417, 25847, 27107, 29717, 33857, 36767, 41357, 51347, 53117, 54917, 56747, 60497
Offset: 1

Author

Vincenzo Librandi, Dec 17 2012

Keywords

Comments

The formula gives consecutive primes for k from 0 to 13.

Crossrefs

Subsequence of A030432, A039949, A141860.

Programs

  • Magma
    [a: n in [1..100] | IsPrime(a) where a is 15*n^2 - 15*n + 17 ];
  • Mathematica
    Select[Table[15 n^2 - 15 n + 17, {n, 1, 100}], PrimeQ]

A247089 Initial members of prime quadruples (p, p+2, p+30, p+32).

Original entry on oeis.org

11, 29, 41, 71, 107, 149, 197, 239, 281, 431, 569, 827, 1019, 1031, 1061, 1289, 1451, 1667, 1997, 2081, 2111, 2237, 2309, 2657, 2969, 3299, 3329, 3359, 3527, 3821, 4019, 4127, 4229, 4241, 4517, 5849, 6269, 6659, 6761, 7457, 7559, 8597
Offset: 1

Author

Karl V. Keller, Jr., Jan 10 2015

Keywords

Comments

Primes p such that (p, p+2) and (p+30, p+32) are twin prime pairs.
This sequence is a subsequence of A001359 (lesser of twin primes).
The subset of terms ending in 1 in this sequence is a subsequence of A132232 (primes, 11 mod 30).
The subset of terms ending in 7 in this sequence is a subsequence of A141860 (primes, 2 mod 15).
The subset of terms ending in 9 in this sequence is a subsequence of A132236 (primes, 29 mod 30).

Examples

			For n=11, the numbers 11, 13, 41, 43, are primes.
		

Crossrefs

Cf. A077800 (twin primes), A001359, A132232, A132236, A141860, A181603 (twins, end 1), A181605 (twins, end 7), A181606 (twins, end 9).

Programs

  • Mathematica
    a247089[n_] := Select[Prime@ Range@ n, And[PrimeQ[# + 2], PrimeQ[# + 30], PrimeQ[# + 32]] &]; a247089[1100] (* Michael De Vlieger, Jan 11 2015 *)
  • Python
    from sympy import isprime
    for n in range(1,10000001,2):
      if isprime(n) and isprime(n+2) and isprime(n+30) and isprime(n+32): print(n,end=', ')
Showing 1-4 of 4 results.