A083371 -id:A083371 - cp's OEIS frontend

A124590 Primes p such that q-p <= 6, where q is the next prime after p.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 97, 101, 103, 107, 109, 127, 131, 137, 149, 151, 157, 163, 167, 173, 179, 191, 193, 197, 223, 227, 229, 233, 239, 251, 257, 263, 269, 271, 277, 281, 307, 311, 313, 331, 347, 349, 353, 367

Offset: 1

N. J. A. Sloane, Dec 19 2006

Goldston, Graham, Pintz, & Yilidirm give a conditional proof that this sequence is infinite; see their Theorem 4. - Charles R Greathouse IV, Jul 31 2013

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
D. A. Goldston, S. W. Graham, J. Pintz, C. Y. Yilidirm, Small gaps between primes or almost primes (2005)
K. Soundararajan, Small gaps between prime numbers: the work of Goldston-Pintz-Yildirim, Bull. Amer. Math. Soc. 44 (2007), pp. 1-18.
Index entries for primes, gaps between

Cf. A083371, A124589, A031924.

v=List([2]);p=3;forprime(q=5,1e3,if(q-p<=6,listput(v,p));p=q);Vec(v) \\ Charles R Greathouse IV, Jul 31 2013

list(lim)=my(v=List(),p=2); forprime(q=3,nextprime(lim\1+1), if(q-p<7, listput(v,p)); p=q); Vec(v) \\ Charles R Greathouse IV, Jan 31 2017

A000040 MINUS A083371. - R. J. Mathar, Jun 15 2008
A124589 UNION A031924. - R. J. Mathar, Jan 23 2022
a(n) >> n log^2 n. - Charles R Greathouse IV, Jan 31 2017

A106628 Anomalous prime numbers.

Original entry on oeis.org

199, 211, 283, 317, 337, 389, 491, 509, 547, 577, 619, 683, 701, 773, 787, 797, 863, 887, 1069, 1109, 1129, 1153, 1163, 1373, 1381, 1409, 1459, 1523, 1531, 1571, 1627, 1637, 1669, 1709, 1723, 1733, 1759, 1831, 1889, 1913, 1933, 1951, 1979, 2003, 2017

Offset: 1

Pahikkala Jussi, May 11 2005

If x and y are two consecutive prime numbers (x < y), Euclid's algorithm gives integers t and d such that tx+dy = 1 = gcd(x, y). The algorithm "Anomalia" gives t and d such that |t+d| is as small as possible (it is often = 1). The prime number x is 'anomalous' iff |t+d| > 1 for x and y.

That is, primes p such that neither q-1 nor q+1 is divisible by q-p, where q is the next prime larger than p. - Charles R Greathouse IV, Aug 20 2017

			a(1) = 199 because -88*199+83*211 = 1, |-88+83| = 5 > 1;
|tx+dy| = 1 for all primes x < 199 (when t and d are determined by the algorithm "Anomalia")

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Subsequence of A083371.

q[x_]:=Module[{y,d},If[!PrimeQ[x],Return[0]];y=NextPrime[x + 1];d=y-x;Mod[y-1, d]!=0 && Mod[y+1, d] != 0];Select[Range[2017],q] (* James C. McMahon, Aug 23 2025 *)

is(x)=if(!isprime(x), return(0)); my(y=nextprime(x+1),d=y-x); (y-1)%d && (y+1)%d \\ Charles R Greathouse IV, Aug 20 2017

Conjecture: a(n) ~ n log n. - Charles R Greathouse IV, Aug 20 2017

A167776 Composite numbers having six composite nearest-neighbors.

Original entry on oeis.org

93, 117, 118, 119, 120, 121, 122, 123, 143, 144, 145, 185, 186, 187, 203, 204, 205, 206, 207, 215, 216, 217, 218, 219, 245, 246, 247, 287, 288, 289, 297, 298, 299, 300, 301, 302, 303, 321, 322, 323, 324, 325, 326, 327, 341, 342, 343, 363, 393, 405, 413, 414

Offset: 1

Juri-Stepan Gerasimov, Nov 11 2009

nonn

Terms lie between primes separated by a gap of at least 8 (see A083371). - David A. Corneth, Jun 24 2016

			a(1)=117 (114,115,116,118,119,120 are composite nearest-neighbors);
a(2)=118 (115,116,117,119,120,121 are composite nearest-neighbors).
There are no primes between primes 241 and 251 which gives a gap of 10 between them. Therefore, all numbers between (inclusive) 241 + 4 and 251 - 4 are terms. - _David A. Corneth_, Jun 24 2016

G. C. Greubel, Table of n, a(n) for n = 1..10000

Cf. A002808, A079364, A083371, A167705.

Select[Range[6!],!PrimeQ[#] && !PrimeQ[#-1] && !PrimeQ[#+1] && !PrimeQ[#-2] && !PrimeQ[#+2] && !PrimeQ[#-3] && !PrimeQ[#+3]&] (* Vladimir Joseph Stephan Orlovsky, Dec 26 2010 *)
Select[Range@ 414, Times @@ Boole@ Map[CompositeQ, Range[# - 3, # + 3]] == 1 &] (* Michael De Vlieger, Jun 24 2016 *)

lista(n) = {forprime(i=2,n+3,g=nextprime(i+1)-i;
for(j=i+4,i+g-4,print1(j", ")))}
a(n) = {forprime(i=88,,g=nextprime(i+1)-i;n-=max(0,g-7);
if(n<=0,return(i+g-4+n)))}
\\ gives the next term larger than n, whether n is a term or not.
nxt(n) = my(p=nextprime(n),g=0); if(p-n>4, n+1, while(1, q=nextprime(p+1); g=q-p; if(g>7, return(p+4), p=q))) \\ David A. Corneth, Jun 24 2016

Corrected (93, 144, 145 inserted) by R. J. Mathar, May 30 2010

A382766 Odd primes p such that p + 4, p + 6 and p + 8 are composite.

Original entry on oeis.org

113, 137, 139, 179, 181, 197, 199, 211, 239, 241, 281, 283, 293, 317, 337, 409, 419, 421, 467, 509, 521, 523, 547, 577, 617, 619, 631, 659, 661, 691, 709, 773, 787, 797, 809, 811, 827, 829, 839, 863, 887, 919, 953, 997, 1019, 1021, 1039, 1049, 1051, 1069

Offset: 1

Michel Eduardo Beleza Yamagishi, Apr 04 2025

nonn

Robert Israel, Table of n, a(n) for n = 1..10000

Cf. A382765, A083371, A124582, A049591, A067774.

P:= select(isprime,{seq(i,i=3..10008,2)}):
R:= P minus (P -~ 4) minus (P -~ 6) minus (P -~ 8):
sort(convert(R,list)); # Robert Israel, Apr 28 2025

Select[Table[
  Module[{p = 2, q},
   While[True, q = 2 n - p; If[PrimeQ[p] && PrimeQ[q], Break[]];
    p = NextPrime[p]]; If[p == 11, q, Nothing]], {n, 2, 1000}], # =!=
   Nothing &]

isok(p) = (p%2) && isprime(p) && !isprime(p+4) && !isprime(p+6) && !isprime(p+8); \\ Michel Marcus, Apr 07 2025

A297709 Table read by antidiagonals: Let b be the number of digits in the binary expansion of n. Then T(n,k) is the k-th odd prime p such that the binary digits of n match the primality of the b consecutive odd numbers beginning with p (or 0 if no such k-th prime exists).

Original entry on oeis.org

3, 5, 7, 7, 13, 3, 11, 19, 5, 23, 13, 23, 11, 31, 7, 17, 31, 17, 47, 13, 5, 19, 37, 29, 53, 19, 11, 3, 23, 43, 41, 61, 37, 17, 0, 89, 29, 47, 59, 73, 43, 29, 0, 113, 23, 31, 53, 71, 83, 67, 41, 0, 139, 31, 19, 37, 61, 101, 89, 79, 59, 0, 181, 47, 43, 7, 41, 67

Offset: 1

Jon E. Schoenfield, Apr 15 2018

For each n >= 1, row n is the union of rows 2n and 2n+1.
Rows with no nonzero terms: 15, 21, 23, 28, 30, 31, ...
Rows whose only nonzero term is 3: 7, 14, 29, 59, 118, 237, 475, 950, 1901, 3802, 7604, ...
Rows whose only nonzero term is 5: 219, 438, 877, 1754, 3508, 7017, 14035, ...
For j = 2, 3, 4, ..., respectively, the first row whose only nonzero term is prime(j) is 7, 219, 2921, ...; is there such a row for every odd prime?

			13 = 1101_2, so row n=13 lists the odd primes p such that the four consecutive odd numbers p, p+2, p+4, and p+6 are prime, prime, composite, and prime, respectively; these are the terms of A022004.
14 = 1110_2, so row n=14 lists the odd primes p such that p, p+2, p+4, and p+6 are prime, prime, prime, and composite, respectively; since there is only one such prime (namely, 3), there is no such 2nd, 3rd, 4th, etc. prime, so the terms in row 14 are {3, 0, 0, 0, ...}.
15 = 1111_2, so row n=15 would list the odd primes p such that p, p+2, p+4, and p+6 are all prime, but since no such prime exists, every term in row 15 is 0.
Table begins:
  n in base|                    k                   |  OEIS
  ---------+----------------------------------------+sequence
  10     2 |   1    2    3    4    5    6    7    8 | number
  =========+========================================+========
   1     1 |   3    5    7   11   13   17   19   23 | A065091
   2    10 |   7   13   19   23   31   37   43   47 | A049591
   3    11 |   3    5   11   17   29   41   59   71 | A001359
   4   100 |  23   31   47   53   61   73   83   89 | A124582
   5   101 |   7   13   19   37   43   67   79   97 | A029710
   6   110 |   5   11   17   29   41   59   71  101 | A001359*
   7   111 |   3    0    0    0    0    0    0    0 |
   8  1000 |  89  113  139  181  199  211  241  283 | A083371
   9  1001 |  23   31   47   53   61   73   83  131 | A031924
  10  1010 |  19   43   79  109  127  163  229  313 |
  11  1011 |   7   13   37   67   97  103  193  223 | A022005
  12  1100 |  29   59   71  137  149  179  197  239 | A210360*
  13  1101 |   5   11   17   41  101  107  191  227 | A022004
  14  1110 |   3    0    0    0    0    0    0    0 |
  15  1111 |   0    0    0    0    0    0    0    0 |
  16 10000 | 113  139  181  199  211  241  283  293 | A124584
  17 10001 |  89  359  389  401  449  479  491  683 | A031926
  18 10010 |  31   47   61   73   83  151  157  167 |
  19 10011 |  23   53  131  173  233  263  563  593 | A049438
  20 10100 |  19   43   79  109  127  163  229  313 |
  21 10101 |   0    0    0    0    0    0    0    0 |
  22 10110 |   7   13   37   67   97  103  193  223 | A022005
  23 10111 |   0    0    0    0    0    0    0    0 |
  24 11000 | 137  179  197  239  281  419  521  617 |
  25 11001 |  29   59   71  149  269  431  569  599 | A049437*
  26 11010 |  17   41  107  227  311  347  461  641 |
  27 11011 |   5   11  101  191  821 1481 1871 2081 | A007530
  28 11100 |   0    0    0    0    0    0    0    0 |
  29 11101 |   3    0    0    0    0    0    0    0 |
  30 11110 |   0    0    0    0    0    0    0    0 |
  31 11111 |   0    0    0    0    0    0    0    0 |
*other than the referenced sequence's initial term 3
.
Alternative version of table:
.
  n in base|primal-|               k              |  OEIS
  ---------+  ity  +------------------------------+  seq.
  10     2 |pattern|   1    2    3    4    5    6 | number
  =========+=======+==============================+========
   1     1 | p     |   3    5    7   11   13   17 | A065091
   2    10 | pc    |   7   13   19   23   31   37 | A049591
   3    11 | pp    |   3    5   11   17   29   41 | A001359
   4   100 | pcc   |  23   31   47   53   61   73 | A124582
   5   101 | pcp   |   7   13   19   37   43   67 | A029710
   6   110 | ppc   |   5   11   17   29   41   59 | A001359*
   7   111 | ppp   |   3    0    0    0    0    0 |
   8  1000 | pccc  |  89  113  139  181  199  211 | A083371
   9  1001 | pccp  |  23   31   47   53   61   73 | A031924
  10  1010 | pcpc  |  19   43   79  109  127  163 |
  11  1011 | pcpp  |   7   13   37   67   97  103 | A022005
  12  1100 | ppcc  |  29   59   71  137  149  179 | A210360*
  13  1101 | ppcp  |   5   11   17   41  101  107 | A022004
  14  1110 | pppc  |   3    0    0    0    0    0 |
  15  1111 | pppp  |   0    0    0    0    0    0 |
  16 10000 | pcccc | 113  139  181  199  211  241 | A124584
  17 10001 | pcccp |  89  359  389  401  449  479 | A031926
  18 10010 | pccpc |  31   47   61   73   83  151 |
  19 10011 | pccpp |  23   53  131  173  233  263 | A049438
  20 10100 | pcpcc |  19   43   79  109  127  163 |
  21 10101 | pcpcp |   0    0    0    0    0    0 |
  22 10110 | pcppc |   7   13   37   67   97  103 | A022005
  23 10111 | pcppp |   0    0    0    0    0    0 |
  24 11000 | ppccc | 137  179  197  239  281  419 |
  25 11001 | ppccp |  29   59   71  149  269  431 | A049437*
  26 11010 | ppcpc |  17   41  107  227  311  347 |
  27 11011 | ppcpp |   5   11  101  191  821 1481 | A007530
  28 11100 | pppcc |   0    0    0    0    0    0 |
  29 11101 | pppcp |   3    0    0    0    0    0 |
  30 11110 | ppppc |   0    0    0    0    0    0 |
  31 11111 | ppppp |   0    0    0    0    0    0 |
.
     *other than the referenced sequence's initial term 3

Cf. A001359, A007530, A022004, A022005, A029710, A031924, A031926, A049437, A049438, A049591, A065091, A124582, A083371, A124584, A210360.

cp's OEIS Frontend

A124583 Duplicate of A083371.

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A124590 Primes p such that q-p <= 6, where q is the next prime after p.

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A106628 Anomalous prime numbers.

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Mathematica

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A167776 Composite numbers having six composite nearest-neighbors.

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A382766 Odd primes p such that p + 4, p + 6 and p + 8 are composite.

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A297709 Table read by antidiagonals: Let b be the number of digits in the binary expansion of n. Then T(n,k) is the k-th odd prime p such that the binary digits of n match the primality of the b consecutive odd numbers beginning with p (or 0 if no such k-th prime exists).

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