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.

A270190 Numbers n for which prime(n+1)-prime(n) is a multiple of three.

Original entry on oeis.org

9, 11, 15, 16, 18, 21, 23, 32, 36, 37, 39, 40, 46, 47, 51, 54, 55, 56, 58, 67, 71, 73, 74, 76, 84, 86, 91, 96, 97, 99, 100, 102, 103, 105, 107, 108, 110, 111, 114, 118, 119, 121, 123, 129, 130, 133, 139, 160, 161, 164, 165, 167, 168, 170, 174, 179, 180, 184, 185, 187, 188, 194, 195, 197, 199, 200, 202, 203, 205, 208, 210
Offset: 1

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Author

Antti Karttunen, Mar 16 2016

Keywords

Comments

Numbers n for which A001223(n) = 0 modulo 3.
See comments in A270189 and A269364.
Equivalently, numbers n for which prime(n+1)-prime(n) is a multiple of six. See A276414 for runs of increasing length of consecutive integers. - M. F. Hasler, Sep 03 2016

Examples

			9 is present as the difference between A000040(9+1) = 29 and A000040(9) = 23 is 6, a multiple of three.
		

Crossrefs

Complement: A270189.
Positions of zeros in A137264.
Left inverse: A269850.

Programs

  • Mathematica
    Select[Range@ 210, Divisible[Prime[# + 1] - Prime@ #, 3] &] (* Michael De Vlieger, Mar 17 2016 *)
    PrimePi/@Select[Partition[Prime[Range[350]],2,1],Divisible[#[[2]]-#[[1]], 3]&][[All,1]] (* Harvey P. Dale, Jul 11 2017 *)
  • PARI
    isok(n) = ((prime(n+1) - prime(n)) % 3) == 0; \\ Michel Marcus, Mar 17 2016

Formula

Other identities. For all n >= 1:
a(n) = A269399(n) + 6.
A269850(a(n)) = n.

A137264 Prime number gaps read modulo 3.

Original entry on oeis.org

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

Views

Author

Noel H. Patson (n.patson(AT)cqu.edu.au), Mar 12 2008

Keywords

Comments

Conjecture: The only digit that is repeated in the sequence is 0 except for n=2 and n=3 where 2 repeats. So 1 may be followed by 2 or 0; 2 may be followed by 1 or 0; 0 may be followed by 0 or 1 or 2. this has been confirmed for the first million prime gaps.
The conjecture is true, because any three numbers whose differences are (1, 1) or (2, 2) will form a complete residue system modulo 3, and hence one of them will be a multiple of 3. - Karl W. Heuer, Mar 16 2016
See comments at A269364. - Antti Karttunen, Mar 17 2016

Crossrefs

Programs

  • Mathematica
    n=1000;(*The length of the list*) Mod[Differences[Table[Prime[i], {i, n}]], 3]
  • Scheme
    (define (A137264 n) (modulo (A001223 n) 3)) ;; Antti Karttunen, Mar 16 2016

A270189 Numbers n for which (prime(n+1)-prime(n)) is not a multiple of three.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 13, 14, 17, 19, 20, 22, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 38, 41, 42, 43, 44, 45, 48, 49, 50, 52, 53, 57, 59, 60, 61, 62, 63, 64, 65, 66, 68, 69, 70, 72, 75, 77, 78, 79, 80, 81, 82, 83, 85, 87, 88, 89, 90, 92, 93, 94, 95, 98, 101, 104, 106, 109, 112, 113, 115, 116, 117, 120, 122, 124, 125
Offset: 1

Views

Author

Antti Karttunen, Mar 16 2016

Keywords

Comments

See A269364 for the effect of the bias that favors these terms over the terms of A270190.

Crossrefs

Complement: A270190.
Disjoint union of A270191 and A270192.
Positions of 1's and 2's in A137264.
Left inverse: A269849.

Programs

  • Mathematica
    Select[Range@ 125, Mod[Prime[# + 1] - Prime@ #, 3] != 0 &] (* Michael De Vlieger, Mar 17 2016 *)
  • PARI
    isok(n) = ((prime(n+1) - prime(n)) % 3) != 0; \\ Michel Marcus, Mar 17 2016

Formula

Other identities. For all n >= 1:
A269849(a(n)) = n.

A270191 Numbers n for which (prime(n+1)-prime(n)) mod 3 = 1.

Original entry on oeis.org

1, 4, 6, 8, 12, 14, 19, 22, 25, 27, 29, 31, 34, 38, 42, 44, 48, 50, 53, 59, 61, 63, 65, 68, 70, 75, 78, 80, 82, 85, 88, 90, 93, 95, 101, 106, 112, 115, 117, 122, 125, 127, 131, 134, 136, 138, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 163, 169, 172, 175, 177, 181, 183, 189, 191, 193, 198, 204, 207, 211, 213, 217, 222
Offset: 1

Views

Author

Antti Karttunen, Mar 16 2016

Keywords

Examples

			1 is present as prime(2)-prime(1) = 3-2 = 1 = 1 mod 3.
4 is present as prime(5)-prime(4) = 11-7 = 4 = 1 mod 3.
		

Crossrefs

Subsequence of A270189.
Positions of ones in A137264.

Programs

  • Mathematica
    Select[Range@ 222, Mod[Prime[# + 1] - Prime@ #, 3] == 1 &] (* Michael De Vlieger, Mar 17 2016 *)
  • PARI
    isok(n) = ((prime(n+1) - prime(n)) % 3) == 1; \\ Michel Marcus, Mar 17 2016
Showing 1-4 of 4 results.