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 1-4 of 4 results.

A086135 Numbers n such that n and n+10 are both prime but are non-consecutive; which means that at least one prime is between n and n+10; it is not identical with A023303 because here the terms of A031928 are missing.

Original entry on oeis.org

3, 7, 13, 19, 31, 37, 43, 61, 73, 79, 97, 103, 127, 157, 163, 223, 229, 271, 307, 349, 373, 379, 433, 439, 457, 499, 607, 643, 673, 733, 751, 853, 877, 937, 967, 1009, 1087, 1093, 1213, 1279, 1291, 1297, 1423, 1429, 1483, 1489, 1543, 1549, 1597, 1609, 1657, 1777
Offset: 1

Views

Author

Labos Elemer, Jul 28 2003

Keywords

Examples

			First deviation from A023303 = {3,7,13,19,31,37,43,61,73,79,97,103,127,139,157,..} is due to the absence of 139=A031928(1).
		

Programs

  • Mathematica
    Do[s=Prime[n]; s1=Prime[n+1]; If[PrimeQ[s+d]&& !Equal[s1-s, d], Print[s]], {n, 1, 1000}]
    Select[Prime[Range[300]],PrimeQ[#+10]&&NextPrime[#]!=(#+10)&] (* Harvey P. Dale, Oct 25 2020 *)

Formula

Complement of a=A031928 with respect to b=A023303: [b]&[nota]: this and A031928 are disjoint, but A031928 is a proper subset of A023303.

A023331 Primes that remain prime through 5 iterations of function f(x) = 2x + 3.

Original entry on oeis.org

47, 67, 1427, 6047, 12097, 16057, 44507, 76537, 92387, 100057, 132707, 209647, 263387, 354247, 407947, 465407, 477727, 507757, 775237, 787477, 788687, 865327, 907367, 955457, 1015517, 1121387, 1178197, 1302277, 1360367, 1524247, 1623707
Offset: 1

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Author

Keywords

Comments

Primes p such that 2*p+3, 4*p+9, 8*p+21, 16*p+45 and 32*p+93 are also prime. - Vincenzo Librandi, Aug 04 2010
Subsequence of A023303. - Michel Marcus, Jun 25 2014

Crossrefs

Cf. A023303 (through 4 iterations).

Programs

  • Magma
    [p: p in PrimesUpTo(2000000) | IsPrime(2*p+3) and IsPrime(4*p+9) and IsPrime(8*p+21) and IsPrime(16*p+45) and IsPrime(32*p+93)]; // Vincenzo Librandi, Aug 04 2010
  • Mathematica
    Select[Prime[Range[20000]], And@@PrimeQ[NestList[2 # + 3 &, #, 5]] &] (* Vincenzo Librandi, Jun 25 2014 *)

A086138 Number of primes between p and p+10 if both p and (p+10) are prime, i.e., number of primes somewhere between 10+A023203(n) and A023203(n).

Original entry on oeis.org

3, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 0, 1, 1, 0, 2, 1, 0, 1, 0, 2, 0, 1, 1, 1, 0, 0, 1, 1, 2, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 2, 2, 0, 1, 1, 1, 0, 0, 0, 2, 1, 0, 0, 1, 0, 1, 1, 2, 0, 2, 1, 0, 2, 1, 1, 1, 1, 1, 0, 1, 0, 0, 1, 0, 1, 2, 0, 1, 2, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 2
Offset: 1

Views

Author

Labos Elemer, Jul 29 2003

Keywords

Examples

			a(n)=0,1,2,3 correspond to {p,p+10} prime-pairs either consecutive ones or those with various d-patterns like as follows: a(n)=0 to cases like 139[10]149; a(n)=2 to 7[4,2,4]17 etc.; a(n)=3 to one case 3[2,2,4,2]13 and a(n)=2 to cases like 31[6,4]37 or 43[4,6]53.
		

Crossrefs

Programs

Extensions

Definition clarified by Harvey P. Dale, Jan 17 2025

A244086 Primes p such that p remains prime through 7 iterations of function f(x) = 2*x + 3.

Original entry on oeis.org

477727, 507757, 30596497, 33145687, 36180527, 61192997, 141339217, 148590307, 193394347, 297180617, 374066267, 395534747, 398001547, 419795137, 488716897
Offset: 1

Views

Author

Vincenzo Librandi, Jun 24 2014

Keywords

Crossrefs

Cf. similar sequences with k iterations: A067076 (k=1), A023242 (k=2), A023273 (k=3), A023303 (k=4), A023331 (k=5), A175160 (k=6), this sequence (k=7).

Programs

  • Magma
    [p: p in PrimesUpTo(600000000) | forall{i: i in [1..7] | IsPrime(2^i*p+3*(2^i-1))}];
  • Mathematica
    Select[Prime[Range[600000]], And@@PrimeQ[NestList[2 # + 3 &, #, 7]] &]

Extensions

Inappropriate MAGMA code simplified and other terms added from Bruno Berselli, Jun 24 2014
Showing 1-4 of 4 results.