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 21 results. Next

A030433 Primes of form 10*k + 9.

Original entry on oeis.org

19, 29, 59, 79, 89, 109, 139, 149, 179, 199, 229, 239, 269, 349, 359, 379, 389, 409, 419, 439, 449, 479, 499, 509, 569, 599, 619, 659, 709, 719, 739, 769, 809, 829, 839, 859, 919, 929, 1009, 1019, 1039, 1049, 1069, 1109, 1129, 1229, 1249, 1259, 1279, 1289
Offset: 1

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Author

Keywords

Comments

Also primes of form 5*k + 4.
5 is quadratic residue of primes of form 10*k-1. - Vincenzo Librandi, Jun 25 2014
Also, primes p such that 5 divides sigma(p), cf. A274397. - M. F. Hasler, Jul 10 2016
Conjecture: Primes p such that ((x+1)^5-1)/x has 2 distinct irreducible factors of degree 2 over GF(p). - Federico Provvedi, Apr 01 2018
The digital root of a(n) is 1, 2, 4, 5, 7 or 8. - Muniru A Asiru, Apr 28 2018
From Jianing Song, Sep 13 2022: (Start)
Primes p such that the ideal (p) factors into two prime ideals in Z[zeta_5], where zeta_5 = exp(2*Pi*i/5). Since Z[zeta_5] is a PID, this is equivalent to saying that this sequence lists primes p that are the product of two non-associate prime elements Z[zeta_5]. In particular, the factorization of p == 4 (mod 5) in Z[zeta_5] coincides with the factorization in Z[(1+sqrt(5))/2] (e.g., 19 = (8+3*sqrt(5))*(8-3*sqrt(5)) is the factorization of 19 in both Z[(1+sqrt(5))/2] and Z[zeta_5]).
Also primes p such that x^4 + x^3 + x^2 + x + 1 factors into two irreducible quadratic polynomials over GF(p) (cf. A327753). (End)

Crossrefs

Programs

  • GAP
    Filtered(List([1..500],n->10*n+9),IsPrime); # Muniru A Asiru, Apr 27 2018
  • Maple
    select(isprime,[seq(10*n+9,n=1..500)]); # Muniru A Asiru, Apr 27 2018
  • Mathematica
    Select[Prime@Range[210], Mod[ #, 10] == 9 &] (* Ray Chandler, Nov 07 2006 *)
    Select[Range[9, 1300, 10], PrimeQ] (* Harvey P. Dale, Jun 01 2012 *)
    Prime@Flatten@Position[Length@FactorList[((1+d)^5-1)/d,Modulus->#]&/@Prime@Range@200,3] (* Federico Provvedi, Apr 04 2018 *)
  • PARI
    select(n->n%10==9, primes(100)) \\ Charles R Greathouse IV, Apr 29 2015
    
  • PARI
    for(n=1, 1e3, if(isprime(p=10*n+9), print1(p, ", "))); \\ Altug Alkan, Apr 19 2018
    

Formula

a(n) = 10*A102700(n) + 9.
Union of A132234 and A132236. - Ray Chandler, Apr 07 2009
Intersection of A000040 and A017377. - Iain Fox, Dec 30 2017

Extensions

Extended by Ray Chandler, Nov 07 2006

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

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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

A132230 Primes congruent to 1 (mod 30).

Original entry on oeis.org

31, 61, 151, 181, 211, 241, 271, 331, 421, 541, 571, 601, 631, 661, 691, 751, 811, 991, 1021, 1051, 1171, 1201, 1231, 1291, 1321, 1381, 1471, 1531, 1621, 1741, 1801, 1831, 1861, 1951, 2011, 2131, 2161, 2221, 2251, 2281, 2311, 2341, 2371, 2521, 2551, 2671
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Comments

Also primes congruent to 1 (mod 15). - N. J. A. Sloane, Jul 11 2008
Primes ending in 1 with (SOD-1)/3 integer where SOD is sum of digits. - Ki Punches, Feb 04 2009

Examples

			From _Muniru A Asiru_, Nov 01 2017: (Start)
31 is a prime and 31 = 30*1 + 1;
61 is a prime and 61 = 30*2 + 1;
151 is a prime and 151 = 30*5 + 1;
211 is a prime and 211 = 30*7 + 1;
241 is a prime and 241 = 30*8 + 1;
271 is a prime and 271 = 30*9 + 1.
(End)
		

Crossrefs

Programs

Formula

a(n) = A111175(n)*30 + 1. - Ray Chandler, Apr 07 2009
Intersection of A030430 and A002476. - Ray Chandler, Apr 07 2009

Extensions

Edited by Ray Chandler, Apr 07 2009

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

A132231 Primes congruent to 7 (mod 30).

Original entry on oeis.org

7, 37, 67, 97, 127, 157, 277, 307, 337, 367, 397, 457, 487, 547, 577, 607, 727, 757, 787, 877, 907, 937, 967, 997, 1087, 1117, 1237, 1297, 1327, 1447, 1567, 1597, 1627, 1657, 1747, 1777, 1867, 1987, 2017, 2137, 2287, 2347, 2377, 2437, 2467, 2557, 2617, 2647
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Comments

Primes ending in 7 with (SOD-1)/3 integer where SOD is sum of digits. - Ki Punches, Feb 07 2009
Intersection of A030432 and A002476. - Ray Chandler, Apr 07 2009
Only from 4927 on, there are more composite numbers than primes in {7+30k}, see A227869. - M. F. Hasler, Nov 02 2013
Terms are non-twin primes A007510, except for 7. - Jonathan Sondow, Oct 27 2017

Crossrefs

Programs

  • Haskell
    a132231 n = a132231_list !! (n-1)
    a132231_list = [x | k <- [0..], let x = 30 * k + 7, a010051' x == 1]
    -- Reinhard Zumkeller, Jul 13 2012
    
  • Magma
    [p: p in PrimesUpTo(3000) | p mod 30 eq 7 ]; // Vincenzo Librandi, Aug 14 2012
    
  • Mathematica
    Select[30*Range[0,100]+7,PrimeQ] (* Harvey P. Dale, Feb 01 2012 *)
    Select[Prime[Range[1000]],MemberQ[{7},Mod[#,30]]&] (* Vincenzo Librandi, Aug 14 2012 *)
  • PARI
    forstep(p=7,1999,30,isprime(p)&&print1(p",")) \\ M. F. Hasler, Nov 02 2013

Formula

a(n) = A158573(n)*30 + 7. - Ray Chandler, Apr 07 2009
a(n) = A211890(4,n-1) for n <= 5. - Reinhard Zumkeller, Jul 13 2012

Extensions

Extended by Ray Chandler, Apr 07 2009

A132232 Primes congruent to 11 (mod 30).

Original entry on oeis.org

11, 41, 71, 101, 131, 191, 251, 281, 311, 401, 431, 461, 491, 521, 641, 701, 761, 821, 881, 911, 941, 971, 1031, 1061, 1091, 1151, 1181, 1301, 1361, 1451, 1481, 1511, 1571, 1601, 1721, 1811, 1871, 1901, 1931, 2081, 2111, 2141, 2351, 2381, 2411, 2441, 2531
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Crossrefs

Programs

Formula

From Ray Chandler, Apr 07 2009: (Start)
a(n) = A158614(n)*30 + 11.
Intersection of A030430 and A007528. (End)

Extensions

Extended by Ray Chandler, Apr 07 2009

A132235 Primes congruent to 23 (mod 30).

Original entry on oeis.org

23, 53, 83, 113, 173, 233, 263, 293, 353, 383, 443, 503, 563, 593, 653, 683, 743, 773, 863, 953, 983, 1013, 1103, 1163, 1193, 1223, 1283, 1373, 1433, 1493, 1523, 1553, 1583, 1613, 1733, 1823, 1913, 1973, 2003, 2063, 2153, 2213, 2243, 2273, 2333, 2393
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Comments

Primes (excluding 3) ending in 3 with (SOD-1)/3 non-integer where SOD is sum of digits. - Ki Punches
The sequence is infinite by Dirichlet's theorem. - Arkadiusz Wesolowski, Apr 02 2014
Terms are non-twin primes A007510. - Omar E. Pol, Jul 25 2019

Crossrefs

Programs

Formula

a(n) = A158791(n)*30 + 23. - Ray Chandler, Apr 07 2009
Intersection of A030431 and A007528. - Ray Chandler, Apr 07 2009

Extensions

Extended by Ray Chandler, Apr 07 2009

A132233 Primes congruent to 13 (mod 30).

Original entry on oeis.org

13, 43, 73, 103, 163, 193, 223, 283, 313, 373, 433, 463, 523, 613, 643, 673, 733, 823, 853, 883, 1033, 1063, 1093, 1123, 1153, 1213, 1303, 1423, 1453, 1483, 1543, 1663, 1693, 1723, 1753, 1783, 1873, 1933, 1993, 2053, 2083, 2113, 2143, 2203, 2293, 2383
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Comments

Primes ending in 3 with (SOD-1)/3 integer where SOD is sum of digits. - Ki Punches
Subsequence of primes of A082369. - Michel Marcus, Jan 23 2016

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(3000) | p mod 30 eq 13 ]; // Vincenzo Librandi, Aug 14 2012
    
  • Maple
    select(isprime, [seq(30*i+13,i=0..1000)]); # Robert Israel, Jan 24 2016
  • Mathematica
    Select[Prime[Range[1000]],MemberQ[{13},Mod[#,30]]&] (* Vincenzo Librandi, Aug 14 2012 *)
  • PARI
    lista(nn) = forprime(p=2, nn, if(p % 30 == 13, print1(p, ", "))); \\ Altug Alkan, Jan 23 2016

Formula

a(n) = A158746(n)*30 + 13. - Ray Chandler, Apr 07 2009
Intersection of A030431 and A002476. - Ray Chandler, Apr 07 2009

Extensions

Extended by Ray Chandler, Apr 07 2009

A132234 Primes congruent to 19 (mod 30).

Original entry on oeis.org

19, 79, 109, 139, 199, 229, 349, 379, 409, 439, 499, 619, 709, 739, 769, 829, 859, 919, 1009, 1039, 1069, 1129, 1249, 1279, 1399, 1429, 1459, 1489, 1549, 1579, 1609, 1669, 1699, 1759, 1789, 1879, 1999, 2029, 2089, 2179, 2239, 2269, 2389, 2539, 2659, 2689
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Comments

Also primes congruent to 4 (mod 15). - N. J. A. Sloane, Jul 11 2008
Primes ending in 9 with (SOD-1)/3 integer where SOD is sum of digits. - Ki Punches

Crossrefs

Programs

Formula

a(n) = A158806(n)*30 + 19. - Chandler
Intersection of A030433 and A002476. - Chandler

Extensions

Extended by Ray Chandler, Apr 07 2009

A132247 Twin primes congruent to {1, 11, 13, 17, 19, 29} mod 30.

Original entry on oeis.org

11, 13, 17, 19, 29, 31, 41, 43, 59, 61, 71, 73, 101, 103, 107, 109, 137, 139, 149, 151, 179, 181, 191, 193, 197, 199, 227, 229, 239, 241, 269, 271, 281, 283, 311, 313, 347, 349, 419, 421, 431, 433, 461, 463, 521, 523, 569, 571, 599, 601, 617, 619, 641, 643
Offset: 1

Views

Author

Omar E. Pol, Aug 18 2007

Keywords

Comments

Twin primes that are greater than 7. - Omar E. Pol, Oct 31 2013

Crossrefs

Formula

a(n) = A001097(n+3). - Michel Marcus, Nov 03 2013
Showing 1-10 of 21 results. Next