A132230 -id:A132230 - cp's OEIS frontend

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

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

Omar E. Pol, Aug 18 2007

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

C. K. Caldwell, The Prime Pages
C. K. Caldwell, Twin Primes
Omar E. Pol, Prime numbers in a sieve with 30 columns
Omar E. Pol, Sobre el patrón de los números primos

Cf. A001097, A039949, A132230, A132232-A132234, A132236, A132238-A132246, A132248-A132259.

a(n) = A001097(n+3). - Michel Marcus, Nov 03 2013

A140444 Primes congruent to 1 (mod 14).

Original entry on oeis.org

29, 43, 71, 113, 127, 197, 211, 239, 281, 337, 379, 421, 449, 463, 491, 547, 617, 631, 659, 673, 701, 743, 757, 827, 883, 911, 953, 967, 1009, 1051, 1093, 1163, 1289, 1303, 1373, 1429, 1471, 1499, 1583, 1597, 1667, 1709, 1723, 1877, 1933, 2003, 2017, 2087

Offset: 1

Juri-Stepan Gerasimov, Jun 26 2008

From Federico Provvedi, May 24 2018: (Start)
Also primes congruent to 1 (mod 7).
For every prime p > 2, primes congruent to 1 (mod p) are also congruent to 1 (mod 2*p).
Conjecture: The monic polynomial P(x) = (x+1)^7/x - 1/x = ((x+1)^7-1)/x is irreducible but factorizable over Galois field (mod a(n)) with exactly 6 distinct irreducible factors of degree 1. Examples:
P(x) == (5 + x) (6 + x) (7 + x) (10 + x) (14 + x) (23 + x)    (mod 29)
P(x) == (3 + x) (9 + x) (23 + x) (28 + x) (33 + x) (40 + x)   (mod 43)
P(x) == (24 + x) (27 + x) (35 + x) (40 + x) (42 + x) (52 + x) (mod 71)
P(x) == (5 + x) (8 + x) (65 + x) (84 + x) (86 + x) (98 + x)   (mod 113)
... (End).
Primes in A131877. - Eric Chen, Jun 14 2018

Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Jorma K. Merikoski, Pentti Haukkanen, and Timo Tossavainen, The congruence x^n = -a^n (mod m): Solvability and related OEIS sequences, Notes. Num. Theor. Disc. Math. (2024) Vol. 30, No. 3, 516-529. See p. 526.

Cf. A045437, A045458, A045471, A045473.
A090613 gives prime index.
Cf. A090614.
Cf. A131877.
Primes congruent to 1 (mod k): A000040 (k=1), A065091 (k=2), A002476 (k=3 and 6), A002144 (k=4), A030430 (k=5 and 10), this sequence (k=7 and 14), A007519 (k=8), A061237 (k=9 and 18), A141849 (k=11 and 22), A068228 (k=12), A268753 (k=13 and 26), A132230 (k=15 and 30), A094407 (k=16), A129484 (k=17 and 34), A141868 (k=19 and 38), A141881 (k=20), A124826 (k=21 and 42), A212374 (k=23 and 46), A107008 (k=24), A141927 (k=25 and 50), A141948 (k=27 and 54), A093359 (k=28), A141977 (k=29 and 58), A142005 (k=31 and 62), A133870 (k=32).

Filtered(Filtered([1..2300],n->n mod 14=1),IsPrime); # Muniru A Asiru, Jun 27 2018

[p: p in PrimesUpTo(3000)|p mod 14 in {1}]; // Vincenzo Librandi, Dec 18 2010

select(isprime,select(n->modp(n,14)=1,[$1..2300])); # Muniru A Asiru, Jun 27 2018

Select[Prime[Range[500]], Mod[#, 14] == 1 &]  (* Harvey P. Dale, Mar 21 2011 *)

is(n)=isprime(n) && n%14==1 \\ Charles R Greathouse IV, Jul 02 2016

a(n) ~ 6n log n. - Charles R Greathouse IV, Jul 02 2016

Simpler definition from N. J. A. Sloane, Jul 11 2008

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

Martin Renner, Feb 11 2017

nonn

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

Muniru A Asiru, Table of n, a(n) for n = 1..10000

Subset of A006512, A181603, A132230, A132243 and A132247.

Cf. A001359, A232880, A232881, A232882, A282321, A282322, A282323, A282324, A060229.

Filtered(List([0..300], k -> 30*k+1), n -> IsPrime(n-2) and IsPrime(n));  # Muniru A Asiru, Mar 05 2018

select(n -> isprime(n-2) and isprime(n), [seq(30*k+1, k=0..300)]); # Muniru A Asiru, Mar 05 2018

1 + Select[30 Range@ 200, AllTrue[# + {-1, 1}, PrimeQ] &] (* Michael De Vlieger, Mar 26 2018 *)

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

A359262 a(n) is the largest number m such that prime(n)^m is in A359260.

Original entry on oeis.org

0, 1, 1, 3, 1, 3, 1, 3, 1, 1, 5, 3, 1, 3, 1, 1, 1, 5, 3, 1, 3, 3, 1, 1, 3, 1, 3, 1, 3, 1, 3, 1, 1, 3, 1, 5, 3, 3, 1, 1, 1, 5, 1, 3, 1, 3, 9, 3, 1, 3, 1, 1, 5, 1, 1, 1, 1, 5, 3, 1, 3, 1, 3, 1, 3, 1, 5, 3, 1, 3, 1, 1, 3, 3, 3, 1, 1, 3, 1, 3, 1, 9, 1, 3, 3, 1, 1

Offset: 1

Amiram Eldar, Dec 23 2022

a(n) is the largest number m such that the arithmetic mean of {1, p, p^2, ..., p^k} is an integer for all k in 1..m.
Apparently, all the terms are of the form prime(k)-2 (A040976). Conjecture: The asymptotic density of the occurrences of prime(k)-2 is (1/s(k-1)-1/s(k)), where s(k) = A005867(k) = phi(prime(k)#), and prime(k)# is the k-th primorial number (A002110).
The sums of the first 10^k terms, for k = 1, 2, ..., are 15, 221, 2291, 23287, 233641, 2337007, 23379901, 233814475, 2338211029, 23382168187, ... . If the mentioned above conjecture is correct, then the asymptotic mean of this sequence is Sum_{k>=1} (prime(k)-2)*(1/s(k-1)-1/s(k)) = 2.33821872365981424748... .
Apparently, the indices of records after n = 1 occur at A000720(A073917(n)) (verified for the first 12 terms of A073917) with record values a(A000720(A073917(n))) = prime(n+1) - 2 (verified for the first 150 terms of A073917).

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A000720, A002110, A040976, A073917, A005867, A359260, A359261.

Cf. A002476, A073102, A132230.

a[n_] := Module[{p = Prime[n], k = 1, r = s = 1}, While[Divisible[s, k], k++; r *= p; s += r]; k - 2]; Array[a, 100]

a(n) = {my(p = prime(n), k = 1, r = s = 1); while(!(s%k), k++; r *= p; s += r); k - 2; }

a(n) >= 1 for n >= 2.
a(n) >= 3 iff prime(n) == 1 (mod 6) (prime(n) is in A002476).
Conjectures:
a(n) >= 5 iff prime(n) == 1 (mod 30) (prime(n) is in A132230).
a(n) >= 9 iff prime(n) == 1 (mod 210) (prime(n) is in A073102).
a(n) >= prime(k) - 2 iff prime(n) == 1 (mod A002110(k-1)).

A228541 Numbers having at least one prime factor of the form 30*k + 1.

Original entry on oeis.org

31, 61, 62, 93, 122, 124, 151, 155, 181, 183, 186, 211, 217, 241, 244, 248, 271, 279, 302, 305, 310, 331, 341, 362, 366, 372, 403, 421, 422, 427, 434, 453, 465, 482, 488, 496, 527, 541, 542, 543, 549, 558, 571, 589, 601, 604, 610, 620, 631, 633, 651, 661, 662

Offset: 1

Arkadiusz Wesolowski, Aug 25 2013

Together with 2, supersequence of A228556.

Conjecture: Numbers m such that abs(Sum_{k=1..m} [k|m]*A008683(k)*(-1)^(k/15)) = 0. - Mats Granvik, Jul 06 2024

			183 = 3*61 is in the sequence because 30*2 + 1 is prime.
211 is in the sequence because it is prime and 211 = 30*7 + 1.

Supersequence of A132230. Cf. A228556.

for(n=31, 662, if(setsearch(Set(factor(n)[, 1]%30), 1)==1, print1(n, ", ")));

A229947 Primes congruent to {1, 11, 13, 17, 19, 29} mod 30.

Original entry on oeis.org

11, 13, 17, 19, 29, 31, 41, 43, 47, 59, 61, 71, 73, 79, 89, 101, 103, 107, 109, 131, 137, 139, 149, 151, 163, 167, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 239, 241, 251, 257, 269, 271, 281, 283, 311, 313, 317, 331, 347, 349, 359, 373, 379, 389

Offset: 1

Omar E. Pol, Oct 27 2013

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

Complement of A132237, primes congruent to 7 or 23 (mod 30), in the set of primes > 5. - M. F. Hasler, Nov 02 2013

Omar E. Pol, Prime numbers in a sieve with 30 columns

Cf. A000040, A001097, A039949, A132230, A132232-A132234, A132236, A132238-A132259, A230462.

[p: p in PrimesUpTo(500) | p mod 30 in {1,11,13,17, 19,29} ]; // Vincenzo Librandi, Apr 05 2015

Select[Flatten[Table[30n + {1, 11, 13, 17, 19, 29}, {n, 0, 11}]], PrimeQ] (* Alonso del Arte, Nov 01 2013 *)
Select[Prime@Range[100], MemberQ[{1, 11, 13, 17, 19, 29}, Mod[#, 30]] &] (* Vincenzo Librandi, Apr 05 2015 *)

is(n)=isprime(n) && setsearch([1,11,13,17,19,29], n%30) \\ Charles R Greathouse IV, Mar 08 2015

a(n) ~ 4/3 n log n. - Charles R Greathouse IV, Mar 08 2015

A263770 Smallest prime q such that (prime(n)^2 + q*prime(n))/(prime(n) + 1) is an integer.

Original entry on oeis.org

7, 5, 7, 17, 13, 29, 19, 41, 73, 31, 97, 191, 43, 89, 97, 109, 61, 311, 137, 73, 149, 241, 337, 181, 197, 103, 313, 109, 331, 229, 257, 397, 139, 281, 151, 457, 317, 821, 337, 349, 181, 547, 193, 389, 199, 401, 1061, 449, 229, 461, 937, 241, 727, 757, 1033, 1321, 271, 1361, 557

Offset: 1

Juri-Stepan Gerasimov, Oct 25 2015

nonn

Least prime q such that q == 1 (mod prime(n) + 1).

Consists of the initial terms of sequences A002476, A002144, A002476, A007519, A068228, A140444, A061237, A141881, A107008, A132230, A133870, A141868, A124826, A142292, A142398, A141948, A088955, A142003, ...

Cf. A263729, A263730, A263769.

Table[q = 2; While[! IntegerQ[(Prime[n]^2 + q Prime@ n)/(Prime@ n + 1)], q = NextPrime@ q]; q, {n, 59}] (* Michael De Vlieger, Oct 26 2015 *)

a(n) = {p = prime(n); q = 2; while ((p^2 + p*q) % (p + 1), q = nextprime(q+1)); q;} \\ Michel Marcus, Oct 26 2015

5 is in this sequence because (prime(2)^2 + 5*prime(2))/(prime(2) + 1) = 6 and 5 is prime.

A167857 Numbers whose divisors are represented by an integer polynomial.

Original entry on oeis.org

1, 2, 3, 5, 7, 9, 10, 11, 13, 17, 19, 22, 23, 25, 29, 31, 34, 37, 41, 43, 46, 47, 49, 53, 55, 58, 59, 61, 67, 71, 73, 79, 82, 83, 85, 89, 91, 94, 97, 101, 103, 106, 107, 109, 113, 115, 118, 121, 127, 131, 133, 137, 139, 142, 145, 149, 151, 157, 163, 166, 167, 169, 171

Offset: 1

T. D. Noe, Nov 13 2009

nonn

That is, these numbers n have the property that there is a polynomial f(x) with integer coefficients whose values at x=0..tau(n)-1 are the divisors of n, where tau(n) is the number of divisors of n.

Every prime has this property, as do 1 and 9, the squares of primes of the form 6k+1, and semiprimes p*q with p and q both primes of the form 3k-1 or 3k+1. Terms of the form p^2*q also appear. We can find terms of the form p^m for any m. For example, 2311^13 is the smallest 13th power that appears. For any m, it seems that p^m appears for p a prime of the form k*m#+1, where m# is the product of the primes up to m. Are there terms with three distinct prime divisors?

			The divisors of 55 are (1, 5, 11, 55). The polynomial 1+15x-17x^2+6x^3 takes these values at x=0..3.

T. D. Noe, Table of n, a(n) for n = 1..1000

Cf. A108164, A108166, A112774 (forms of semiprimes)
Cf. A002476 (primes of the form 6k+1)
Cf. A132230 (primes of the form 30k+1)
Cf. A073103 (primes of the form 210k+1)
Cf. A073917 (least prime of the form k*prime(n)#+1)

Select[Range[1000], And @@ IntegerQ /@ CoefficientList[Expand[InterpolatingPolynomial[Divisors[ # ], x+1]], x] &]

is(n)=my(d=divisors(n));denominator(content(polinterpolate([0..#d-1],d))) == 1 \\ Charles R Greathouse IV, Jan 29 2016

A260940 a(n) is the smallest index j>n such that g(j)=0 for the sequence g defined (for indices > n) by g(n+1)=n and g(i) = g(i-1) - gcd(i,g(i-1)).

Original entry on oeis.org

3, 5, 7, 7, 11, 13, 13, 17, 19, 19, 23, 19, 21, 29, 31, 31, 31, 37, 37, 41, 43, 43, 47, 43, 43, 53, 43, 41, 59, 61, 61, 61, 67, 67, 71, 73, 73, 71, 79, 79, 83, 79, 79, 89, 79, 79, 79, 97, 97, 101, 103, 103, 107, 109, 109, 113, 109, 109, 113, 109

Offset: 1

Moritz Firsching, Aug 04 2015

nonn

a(n) is prime for all n<=10^10 except a(13)=21.
a(n) <= 2n + 1.
a(n) = 2n + 1 if and only if 2n + 1 is prime.
a(n) = 2n - 1 if and only if 2n - 1 is a prime and 2n - 1 = 1 mod 6.
a(n) = 2n - 3 if and only if 2n - 3 is a prime and 2n - 3 = 1 mod 30.

Moritz Firsching, Table of n, a(n) for n = 1..9999

Cf. A002476, A132230, A261301.

A186253(n) is a^n(2) where a^n denotes the n-th composition.

a(last_a) = {
  local(A=last_a,B=last_a,C=2*last_a+1);
  while(A>0,
    D=divisors(C);
    k1=10*D[2];
    for(j=2,matsize(D)[2],d=D[j];k=((A+1-B+d)/2)%d;
      if(k==0,k=d); if(k<=k1,k1=k;d1=d));
    if(k1-1+d1==A,B=B+1);
    A = max(A-(k1-1)-d1,0);
    B = B + k1;
    C = C - (d1 - 1);
  );
  return(B);
}
a(n)={
my(A=n, B=n, C=2*n+1);
while(A>0,
my(k1=oo,d1);
fordiv(C,d,
if(d==1,next);
my(k=((A+1-B+d)/2)%d);
if(k==0, k=d);
if(k<=k1, k1=k; d1=d)
);
A -= k1 - 1 + d1;
B += k1 + (A==0);
C -= d1 - 1;
);
B;
} \\ Charles R Greathouse IV, Nov 04 2015

def a(n):
    g=n
    n+=1
    while(g!=0):
        g=g-gcd(n,g)
        n+=1
    return n

A284659 Numbers n such that numbers 30(n+k) + 1 are prime for k=0..5.

Original entry on oeis.org

18, 74, 4386, 4505, 9314, 10357, 21095, 29621, 38784, 102463, 105200, 116134, 163300, 179967, 186918, 210515, 252830, 348709, 354022, 362345, 396820, 400915, 431568, 438862, 457748, 464118, 470852, 477341, 493070

Offset: 1

Zak Seidov, Mar 31 2017

nonn

Numbers n through n+5 are terms in A111175. There are no cases of 7 consecutive numbers in A111175.

All terms are congruent to 4 mod 7.

			a(1)=18 because 1 + 30*k for k=18..23 are 541, 571, 601, 631, 661, 691 all primes: A000040(k) for k={100, 105, 110, 115, 121, 125}.

Robert Israel, Table of n, a(n) for n = 1..1000
Index entries for primes in AP

Cf. A111175, A132230.

filter:= t -> andmap(isprime, [seq(30*(t+k)+1, k=0..5)]):
select(filter, [seq(seq(77*k + i,i=[18,39,53,60,74]),k=0..10000)]); # Robert Israel, Apr 04 2017

Select[Range[18, 1000000, 7], PrimeQ[1 + 30*#] && PrimeQ[1 + 30*(# + 1)] && PrimeQ[1 + 30*(# + 2)] && PrimeQ[1 + 30*(# + 3)] && PrimeQ[1 + 30*(# + 4)] && PrimeQ[1 + 30*(# + 5)] &]
Select[Range[4,10^6,7],AllTrue[30(#+Range[0,5])+1,PrimeQ]&] (* Harvey P. Dale, Dec 03 2023 *)

cp's OEIS Frontend

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

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A140444 Primes congruent to 1 (mod 14).

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

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A359262 a(n) is the largest number m such that prime(n)^m is in A359260.

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A228541 Numbers having at least one prime factor of the form 30*k + 1.

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A229947 Primes congruent to {1, 11, 13, 17, 19, 29} mod 30.

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A263770 Smallest prime q such that (prime(n)^2 + q*prime(n))/(prime(n) + 1) is an integer.

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A167857 Numbers whose divisors are represented by an integer polynomial.

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