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 69 results. Next

A095023 Number of 5k+3 primes (A030431) in range ]2^n,2^(n+1)].

Original entry on oeis.org

1, 0, 1, 1, 2, 4, 5, 11, 18, 36, 63, 117, 220, 407, 760, 1435, 2682, 5074, 9683, 18392, 35113, 67054, 128503, 246433, 473717, 911310, 1756933, 3390711, 6551833, 12673497, 24546404, 47584981, 92331321, 179315178, 348550417, 678028865, 1319937828, 2571418193
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Extensions

a(34)-a(38) from Amiram Eldar, Jun 12 2024

A129078 Prime numbers that are the sum of consecutive prime numbers with the final digit 3 (primes in A030431).

Original entry on oeis.org

3, 1259, 51241, 81749, 230149, 245621, 253567, 269879, 286801, 331301, 482731, 540041, 551917, 564013, 625943, 638669, 746777, 975427, 1093129, 1145537, 1181149, 1272679, 1528187, 1569479, 1675679, 1741517, 1970867, 2066951
Offset: 1

Views

Author

Tomas Xordan, May 11 2007

Keywords

Examples

			a(2)=1259 because 1259=A030431(1)+ A030431(2)+A030431(3)+A030431(4)+ A030431(5)+A030431(6)+A030431(7)+ A030431(8)+A030431(9)+A030431(10)+A030431(11)+A030431(12)+A030431(13)= 3+ 13+ 23+ 43+ 53+ 73+ 83+ 103+ 113+ 163+ 173+ 193+ 223 and 1259 is a prime number.
		

Crossrefs

Programs

  • Mathematica
    Select[Accumulate[Select[10Range[0,1500]+3,PrimeQ]],PrimeQ]  (* Harvey P. Dale, Apr 06 2011 *)

Formula

a(n)=A030431(1)+A030431(2)+...+A030431(x); a is a prime number.

A007528 Primes of the form 6k-1.

Original entry on oeis.org

5, 11, 17, 23, 29, 41, 47, 53, 59, 71, 83, 89, 101, 107, 113, 131, 137, 149, 167, 173, 179, 191, 197, 227, 233, 239, 251, 257, 263, 269, 281, 293, 311, 317, 347, 353, 359, 383, 389, 401, 419, 431, 443, 449, 461, 467, 479, 491, 503, 509, 521, 557, 563, 569, 587
Offset: 1

Views

Author

Keywords

Comments

For values of k see A024898.
Also primes p such that p^q - 2 is not prime where q is an odd prime. These numbers cannot be prime because the binomial p^q = (6k-1)^q expands to 6h-1 some h. Then p^q-2 = 6h-1-2 is divisible by 3 thus not prime. - Cino Hilliard, Nov 12 2008
a(n) = A211890(3,n-1) for n <= 4. - Reinhard Zumkeller, Jul 13 2012
There exists a polygonal number P_s(3) = 3s - 3 = a(n) + 1. These are the only primes p with P_s(k) = p + 1, s >= 3, k >= 3, since P_s(k) - 1 is composite for k > 3. - Ralf Steiner, May 17 2018
From Bernard Schott, Feb 14 2019: (Start)
A theorem due to Andrzej Mąkowski: every integer greater than 161 is the sum of distinct primes of the form 6k-1. Examples: 162 = 5 + 11 + 17 + 23 + 47 + 59; 163 = 17 + 23 + 29 + 41 + 53. (See Sierpiński and David Wells.)
{2,3} Union A002476 Union {this sequence} = A000040.
Except for 2 and 3, all Sophie Germain primes are of the form 6k-1.
Except for 3, all the lesser of twin primes are also of the form 6k-1.
Dirichlet's theorem on arithmetic progressions states that this sequence is infinite. (End)
For all elements of this sequence p=6*k-1, there are no (x,y) positive integers such that k=6*x*y-x+y. - Pedro Caceres, Apr 06 2019

References

  • M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 870.
  • A. Mąkowski, Partitions into unequal primes, Bull. Acad. Polon. Sci. Sér. Sci. Math. Astr. Phys. 8 (1960), 125-126.
  • Wacław Sierpiński, Elementary Theory of Numbers, p. 144, Warsaw, 1964.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Books, Revised edition, 1997, p. 127.

Crossrefs

Intersection of A016969 and A000040.
Prime sequences A# (k,r) of the form k*n+r with 0 <= r <= k-1 (i.e., primes == r (mod k), or primes p with p mod k = r) and gcd(r,k)=1: A000040 (1,0), A065091 (2,1), A002476 (3,1), A003627 (3,2), A002144 (4,1), A002145 (4,3), A030430 (5,1), A045380 (5,2), A030431 (5,3), A030433 (5,4), A002476 (6,1), this sequence (6,5), A140444 (7,1), A045392 (7,2), A045437 (7,3), A045471 (7,4), A045458 (7,5), A045473 (7,6), A007519 (8,1), A007520 (8,3), A007521 (8,5), A007522 (8,7), A061237 (9,1), A061238 (9,2), A061239 (9,4), A061240 (9,5), A061241 (9,7), A061242 (9,8), A030430 (10,1), A030431 (10,3), A030432 (10,7), A030433 (10,9), A141849 (11,1), A090187 (11,2), A141850 (11,3), A141851 (11,4), A141852 (11,5), A141853 (11,6), A141854 (11,7), A141855 (11,8), A141856 (11,9), A141857 (11,10), A068228 (12,1), A040117 (12,5), A068229 (12,7), A068231 (12,11).
Cf. A034694 (smallest prime == 1 (mod n)).
Cf. A038700 (smallest prime == n-1 (mod n)).
Cf. A038026 (largest possible value of smallest prime == r (mod n)).
Cf. A001359 (lesser of twin primes), A005384 (Sophie Germain primes).

Programs

  • GAP
    Filtered(List([1..100],n->6*n-1),IsPrime); # Muniru A Asiru, May 19 2018
  • Haskell
    a007528 n = a007528_list !! (n-1)
    a007528_list = [x | k <- [0..], let x = 6 * k + 5, a010051' x == 1]
    -- Reinhard Zumkeller, Jul 13 2012
    
  • Maple
    select(isprime,[seq(6*n-1,n=1..100)]); # Muniru A Asiru, May 19 2018
  • Mathematica
    Select[6 Range[100]-1,PrimeQ]  (* Harvey P. Dale, Feb 14 2011 *)
  • PARI
    forprime(p=2, 1e3, if(p%6==5, print1(p, ", "))) \\ Charles R Greathouse IV, Jul 15 2011
    
  • PARI
    forprimestep(p=5,1000,6, print1(p", ")) \\ Charles R Greathouse IV, Mar 03 2025
    

Formula

A003627 \ {2}. - R. J. Mathar, Oct 28 2008
Conjecture: Product_{n >= 1} ((a(n) - 1) / (a(n) + 1)) * ((A002476(n) + 1) / (A002476(n) - 1)) = 3/4. - Dimitris Valianatos, Feb 11 2020
From Vaclav Kotesovec, May 02 2020: (Start)
Product_{k>=1} (1 - 1/a(k)^2) = 9*A175646/Pi^2 = 1/1.060548293.... =4/(3*A333240).
Product_{k>=1} (1 + 1/a(k)^2) = A334482.
Product_{k>=1} (1 - 1/a(k)^3) = A334480.
Product_{k>=1} (1 + 1/a(k)^3) = A334479. (End)
Legendre symbol (-3, a(n)) = -1 and (-3, A002476(n)) = +1, for n >= 1. For prime 3 one sets (-3, 3) = 0. - Wolfdieter Lang, Mar 03 2021

A030432 Primes of form 10n+7.

Original entry on oeis.org

7, 17, 37, 47, 67, 97, 107, 127, 137, 157, 167, 197, 227, 257, 277, 307, 317, 337, 347, 367, 397, 457, 467, 487, 547, 557, 577, 587, 607, 617, 647, 677, 727, 757, 787, 797, 827, 857, 877, 887, 907, 937, 947, 967, 977, 997, 1087, 1097, 1117, 1187, 1217, 1237
Offset: 1

Views

Author

Keywords

Comments

Union of A132231 and A039949. - Ray Chandler, Apr 07 2009
5 is not quadratic residue of primes of this form. - Vincenzo Librandi, Jun 25 2014
Also primes of the form 5n+2 with positive n. - Danny Rorabaugh, Feb 20 2016
Intersection of A000040 and A017353. - Iain Fox, Dec 30 2017

Crossrefs

Cf. A030430 (10n+1), A030431 (10n+3), A030433 (10n+9).

Programs

  • Magma
    [n: n in [7..1240 by 10] | IsPrime(n)]; // Bruno Berselli, Apr 06 2011
    
  • Mathematica
    Select[Prime@Range[210], Mod[ #, 10] == 7 &] (* Ray Chandler, Nov 07 2006 *)
  • PARI
    is(n)=n%10==7 && isprime(n) \\ Charles R Greathouse IV, Jul 01 2013
    
  • PARI
    lista(nn) = forprime(p=7, nn, if(p%10==7, print1(p, ", "))) \\ Iain Fox, Dec 30 2017
    
  • Sage
    [10*n+7 for n in range(124) if is_prime(10*n+7)] # Danny Rorabaugh, Feb 20 2016

Formula

a(n) = 10*A102342(n) + 7.
a(n) ~ 4n log n. - Charles R Greathouse IV, Jul 01 2013

Extensions

Extended by Ray Chandler, Nov 07 2006

A244763 Prime numbers ending in the prime number 13.

Original entry on oeis.org

13, 113, 313, 613, 1013, 1213, 1613, 1913, 2113, 2213, 2713, 3313, 3413, 3613, 4013, 4513, 4813, 5113, 5413, 5813, 6113, 7013, 7213, 8513, 8713, 9013, 9413, 9613, 10313, 10513, 10613, 11113, 11213, 11813, 12113, 12413, 12613, 12713, 13313, 13513, 13613, 13913
Offset: 1

Views

Author

Vincenzo Librandi, Jul 06 2014

Keywords

Comments

Also primes of the form 100*n+13. Subsequence of A141885, A141937, A166573.

Crossrefs

Cf. Prime numbers ending in the prime number k: A030431 (k=3), A030432 (k=7), A167442 (k=11), this sequence (k=13), A244764 (k=17), A244765 (k=19), A244766 (k=23), A244767 (k=29), A167388 (k=31), A244768 (k=37), A167443 (k=41), A244769 (k=43), A244770 (k=47), A244771 (k=53), A244772 (k=59), A167445 (k=61), A244773 (k=67), A167441 (k=71), A244774 (k=73), A244775 (k=79), A244776 (k=83), A244777 (k=89), A244778 (k=97), A167626 (k=101), A167627 (k=163).

Programs

  • Magma
    [n: n in PrimesUpTo(14000) | n mod 100 eq 13];
    
  • Maple
    select(isprime, [13+100*n $ n=0..1000]); # Robert Israel, Jul 06 2014
  • Mathematica
    Select[Prime[Range[5, 2000]], Take[IntegerDigits[#], -2]=={1, 3}&]
  • PARI
    select(x->(x % 100)==13, primes(2000)) \\ Michel Marcus, Jul 06 2014
    
  • Sage
    [p for p in primes(14000) if mod(p,100) == 13] # Bruno Berselli, Jul 07 2014

A105854 Primes of the form 20*k + 3.

Original entry on oeis.org

3, 23, 43, 83, 103, 163, 223, 263, 283, 383, 443, 463, 503, 523, 563, 643, 683, 743, 823, 863, 883, 983, 1063, 1103, 1123, 1163, 1223, 1283, 1303, 1423, 1483, 1523, 1543, 1583, 1663, 1723, 1783, 1823, 2003, 2063, 2083, 2143, 2203, 2243, 2383, 2423, 2503, 2543
Offset: 1

Views

Author

Zak Seidov, May 05 2005

Keywords

Comments

Cf. A030431: Primes of the form 10*k + 3.

Crossrefs

Programs

  • Magma
    [n: n in PrimesUpTo(2600) | IsDivisibleBy(n-3,20)];  // Bruno Berselli, Apr 05 2011
    
  • Magma
    [ a: n in [0..250] | IsPrime(a) where a is 20*n+3 ]; // Vincenzo Librandi, Apr 06 2011
  • Mathematica
    Select[Range[3, 2003, 20], PrimeQ[ # ]&]

Extensions

More terms from N. J. A. Sloane, Jul 11 2008

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

A141849 Primes congruent to 1 mod 11.

Original entry on oeis.org

23, 67, 89, 199, 331, 353, 397, 419, 463, 617, 661, 683, 727, 859, 881, 947, 991, 1013, 1123, 1277, 1321, 1409, 1453, 1607, 1783, 1871, 2003, 2069, 2113, 2179, 2267, 2311, 2333, 2377, 2399, 2531, 2663, 2707, 2729, 2861, 2927, 2971, 3037, 3169, 3191, 3257
Offset: 1

Views

Author

N. J. A. Sloane, Jul 11 2008

Keywords

Comments

Conjecture: Also primes p such that ((x+1)^11-1)/x has 10 distinct irreducible factors of degree 1 over GF(p). - Federico Provvedi, Apr 17 2018
Primes congruent to 1 mod 22. - Chai Wah Wu, Apr 28 2025

Crossrefs

Prime sequences A# (k,r) of the form k*n+r with 0 <= r <= k-1 (i.e., primes == r (mod k), or primes p with p mod k = r) and gcd(r,k)=1: A000040 (1,0), A065091 (2,1), A002476 (3,1), A003627 (3,2), A002144 (4,1), A002145 (4,3), A030430 (5,1), A045380 (5,2), A030431 (5,3), A030433 (5,4), A002476 (6,1), A007528 (6,5), A140444 (7,1), A045392 (7,2), A045437 (7,3), A045471 (7,4), A045458 (7,5), A045473 (7,6), A007519 (8,1), A007520 (8,3), A007521 (8,5), A007522 (8,7), A061237 (9,1), A061238 (9,2), A061239 (9,4), A061240 (9,5), A061241 (9,7), A061242 (9,8), A030430 (10,1), A030431 (10,3), A030432 (10,7), A030433 (10,9), this sequence (11,1), A090187 (11,2), A141850 (11,3), A141851 (11,4), A141852 (11,5), A141853 (11,6), A141854 (11,7), A141855 (11,8), A141856 (11,9), A141857 (11,10), A068228 (12,1), A040117 (12,5), A068229 (12,7), A068231 (12,11).
Cf. A034694 (smallest prime == 1 (mod n)).
Cf. A038700 (smallest prime == n-1 (mod n)).
Cf. A038026 (largest possible value of smallest prime == r (mod n)).

Programs

Formula

a(n) ~ 10n log n. - Charles R Greathouse IV, Jul 02 2016

A385800 Primes having only {6, 8, 9} as digits.

Original entry on oeis.org

89, 6689, 6869, 6899, 8669, 8689, 8699, 8969, 8999, 9689, 66889, 68669, 68699, 68899, 69899, 86689, 86869, 86969, 88969, 89669, 89689, 89899, 89989, 96989, 98669, 98689, 98869, 98899, 98999, 99689, 99989, 666889, 666989, 668699, 668869, 668989, 668999, 669689, 669869
Offset: 1

Views

Author

Jason Bard, Jul 14 2025

Keywords

Crossrefs

Subsequence of A030431, A106111.
Supersequence of A020472.

Programs

  • Magma
    [p: p in PrimesUpTo(10^6) | Set(Intseq(p)) subset [6, 8, 9]];
    
  • Mathematica
    Flatten[Table[Select[FromDigits /@ Tuples[{6, 8, 9}, n], PrimeQ], {n, 7}]]
  • PARI
    primes_with(, 1, [6, 8, 9]) \\ uses function in A385776
  • Python
    print(list(islice(primes_with("689"), 41))) # uses function/imports in A385776
    

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
Showing 1-10 of 69 results. Next