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 77 results. Next

A129081 Primes appearing in partial sums of A030433 (primes ending in 9).

Original entry on oeis.org

19, 107, 523, 1279, 1787, 4091, 16103, 18041, 46889, 68437, 104561, 155443, 161641, 174367, 187573, 303473, 330587, 359231, 419929, 430517, 634793, 878939, 974507, 1469753, 1510319, 1700851, 1902653, 2836961, 2982841, 3476299, 3807589
Offset: 1

Views

Author

Tomas Xordan, May 11 2007

Keywords

Examples

			a(5) = 1787 because 1787 = A030433(1) + A030433(2) + A030433(3) + A030433(4) + A030433(5) + A030433(6) + A030433(7) + A030433(8) + A030433(9) + A030433(10) + A030433(11) + A030433(12) + A030433(13) = 19 + 29 + 59 + 79 + 89 + 109 + 139 + 149 + 179 + 199 + 229 + 239 + 269; and 1787 is a prime number.
		

Crossrefs

Programs

  • GAP
    P:=Filtered(List([1..5*10^5],n->10*n+9),IsPrime);;
    a:=Filtered(List([1..Length(P)],i->Sum([1..i],k->P[k])),IsPrime); # Muniru A Asiru, Apr 28 2018
  • Mathematica
    With[{pr9s=Select[Prime[Range[3000]],Last[IntegerDigits[#]]==9&]}, Select[ Accumulate[ pr9s],PrimeQ]] (* Harvey P. Dale, Dec 31 2011 *)
  • PARI
    {s=0; forprime(p=2, 17300, if(p%10==9, s+=p; if(isprime(s), print1(s, ","))))} /* Klaus Brockhaus, May 13 2007 */
    

Formula

a(n) = A030433(1)+A030433(2)+...+A030433(x); a is a prime number.

Extensions

Entries checked by Klaus Brockhaus, May 13 2007
Better description from Harvey P. Dale, Dec 31 2011

A095024 Number of 5k+4 primes (A030433) in range ]2^n,2^(n+1)].

Original entry on oeis.org

0, 0, 0, 2, 1, 3, 6, 12, 16, 35, 63, 115, 216, 399, 754, 1418, 2705, 5077, 9667, 18403, 35047, 67045, 128509, 246330, 473457, 911409, 1756619, 3390969, 6551382, 12675118, 24544171, 47584397, 92329550, 179316852, 348547854, 678021581, 1319945483, 2571395286
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Extensions

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

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

A045468 Primes congruent to {1, 4} mod 5.

Original entry on oeis.org

11, 19, 29, 31, 41, 59, 61, 71, 79, 89, 101, 109, 131, 139, 149, 151, 179, 181, 191, 199, 211, 229, 239, 241, 251, 269, 271, 281, 311, 331, 349, 359, 379, 389, 401, 409, 419, 421, 431, 439, 449, 461, 479, 491
Offset: 1

Views

Author

Keywords

Comments

Rational primes that decompose in the field Q(sqrt(5)). - N. J. A. Sloane, Dec 26 2017
These are also primes p that divide Fibonacci(p-1). - Jud McCranie
Primes ending in 1 or 9. - Lekraj Beedassy, Oct 27 2003
Also primes p such that p divides 5^(p-1)/2 - 4^(p-1)/2. - Cino Hilliard, Sep 06 2004
Primes p such that the polynomial x^2-x-1 mod p has 2 distinct zeros. - T. D. Noe, May 02 2005
Same as A038872, apart from the term 5. - R. J. Mathar, Oct 18 2008
Appears to be the primes p such that p^6 mod 210 = 1. - Gary Detlefs, Dec 29 2011
Primes in A047209, also in A090771. - Reinhard Zumkeller, Jan 07 2012
Primes p such that p does not divide Sum_{i=1..p} Fibonacci(i)^2. The sum is A001654(p). - Arkadiusz Wesolowski, Jul 23 2012
Primes congruent to {1, 9} mod 10. Legendre symbol (5, a(n)) = +1. For prime 5 this symbol (5, 5) is set to 0, and (5, prime) = -1 for prime == {3, 7} (mod 10), given in A003631. - Wolfdieter Lang, Mar 05 2021

References

  • Hardy and Wright, An Introduction to the Theory of Numbers, Chap. X, p. 150, Oxford University Press, Fifth edition.

Crossrefs

Programs

  • Haskell
    a045468 n = a045468_list !! (n-1)
    a045468_list = [x | x <- a047209_list, a010051 x == 1]
    -- Reinhard Zumkeller, Jan 07 2012
    
  • Magma
    [ p: p in PrimesUpTo(1000) | p mod 5 in {1,4} ]; // Vincenzo Librandi, Aug 13 2012
  • Maple
    for n from 1 to 500 do if(isprime(n)) and (n^6 mod 210=1) then print(n) fi od;  # Gary Detlefs, Dec 29 2011
  • Mathematica
    lst={};Do[p=Prime[n];If[Mod[p,5]==1||Mod[p,5]==4,AppendTo[lst,p]],{n,6!}];lst (* Vladimir Joseph Stephan Orlovsky, Feb 26 2009 *)
    Select[Prime[Range[200]],MemberQ[{1,4},Mod[#,5]]&] (* Vincenzo Librandi, Aug 13 2012 *)
  • PARI
    list(lim)=select(n->n%5==1||n%5==4,primes(primepi(lim))) \\ Charles R Greathouse IV, Jul 25 2011
    

A132236 Primes congruent to 29 (mod 30).

Original entry on oeis.org

29, 59, 89, 149, 179, 239, 269, 359, 389, 419, 449, 479, 509, 569, 599, 659, 719, 809, 839, 929, 1019, 1049, 1109, 1229, 1259, 1289, 1319, 1409, 1439, 1499, 1559, 1619, 1709, 1889, 1949, 1979, 2039, 2069, 2099, 2129, 2309, 2339, 2399, 2459, 2549, 2579
Offset: 1

Views

Author

Omar E. Pol, Aug 15 2007

Keywords

Comments

Primes ending in 9 with (SOD-1)/3 non-integer where SOD is sum of digits. - Ki Punches

Crossrefs

Programs

Formula

a(n) = A158850(n)*30 + 29. - Chandler
Intersection of A030433 and A007528. - Chandler

Extensions

Extended by Ray Chandler, Apr 07 2009

A074822 Primes p such that p + 4 is prime and p == 9 (mod 10).

Original entry on oeis.org

19, 79, 109, 229, 349, 379, 439, 499, 739, 769, 859, 1009, 1279, 1429, 1489, 1549, 1579, 1609, 1999, 2239, 2269, 2389, 2539, 2659, 2689, 2749, 3019, 3079, 3319, 3529, 3919, 4129, 4519, 4639, 4729, 4789, 4969, 4999, 5479, 5569, 5689, 5779, 5839, 6199
Offset: 1

Views

Author

Roger L. Bagula, Sep 30 2002

Keywords

Comments

From Rémi Eismann, May 14 2006; May 04 2007: (Start)
Also primes for which k is equal to 5 in A117078. Examples: prime(9) = prime(8) + (prime(8) mod 5) = 19 + (19 mod 5)=23; prime(23) = prime(22) + (prime(22) mod 5) = 79 + (79 mod 5)=83; prime(1359) = prime(1358) + (prime(1358) mod 5) = 11239+ (11239 mod 5)=11243.
The prime numbers in this sequence are of the form (10i-1) with i=(level(n)+1)/2, level(n) defined in A117563.
Consider A117078: a(n) = smallest k such that prime(n+1) = prime(n) + (prime(n) mod k), or 0 if no such k exists. Sequence gives values of prime(n) for which k=5. (End)
p is the lesser member of cousin primes (p,p+4) such that p == 9 (mod 10). - Muniru A Asiru, Jul 03 2017

Crossrefs

Intersection of A023200 and A030433.

Programs

  • Mathematica
    Prime[ Select[ Range[1000], Prime[ # ] + 4 == Prime[ # + 1] && Mod[ Prime[ # ], 10] == 9 & ]]
    Transpose[Select[Partition[Prime[Range[820]],2,1],Last[#]-First[#] == 4 && Mod[ First[ #],10]==9&]][[1]] (* Harvey P. Dale, Oct 20 2011 *)
  • PARI
    is(n)=n%30==19 && isprime(n+4) && isprime(n) \\ Charles R Greathouse IV, Jul 12 2017
    
  • PARI
    list(lim)=my(v=List(),p=19); forprime(q=23,lim+4, if(q-p==4 && p%30==19, listput(v,p)); p=q); Vec(v) \\ Charles R Greathouse IV, Jul 12 2017

Extensions

Edited by Robert G. Wilson v and N. J. A. Sloane, Oct 03 2002
Entry revised by N. J. A. Sloane, Feb 24 2007

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

A102700 Numbers k such that 10*k + 9 is prime.

Original entry on oeis.org

1, 2, 5, 7, 8, 10, 13, 14, 17, 19, 22, 23, 26, 34, 35, 37, 38, 40, 41, 43, 44, 47, 49, 50, 56, 59, 61, 65, 70, 71, 73, 76, 80, 82, 83, 85, 91, 92, 100, 101, 103, 104, 106, 110, 112, 122, 124, 125, 127, 128, 131, 139, 140, 142, 143, 145, 148, 149, 154, 155, 157, 160, 161
Offset: 1

Views

Author

Parthasarathy Nambi, Feb 04 2005

Keywords

Examples

			10*1 + 9 = 19 (prime);
10*40 + 9 = 409 (prime);
10*70 + 9 = 709 (prime).
		

Crossrefs

Programs

Extensions

Edited and extended by Ray Chandler, Nov 07 2006

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
Showing 1-10 of 77 results. Next