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 1-5 of 5 results.

A175914 Primes p such that p+2*q is prime, where q is the prime after p.

Original entry on oeis.org

3, 5, 7, 11, 13, 41, 43, 59, 89, 101, 103, 113, 127, 179, 181, 191, 193, 223, 241, 269, 277, 293, 307, 311, 313, 337, 359, 421, 431, 479, 491, 521, 599, 613, 631, 673, 773, 787, 821, 823, 863, 881, 883, 907, 911, 919, 929, 937, 953, 967, 1019, 1021, 1039, 1061, 1109, 1151, 1171
Offset: 1

Views

Author

Zak Seidov, Dec 05 2010

Keywords

Comments

A174915 gives lesser of twin primes in this sequence.
Values of p+2*q are in A094105. [Zak Seidov, Sep 07 2012]

Examples

			3 and 5 are consecutive primes, and 3+2*5 = 13 is prime. Hence 3 is in the sequence.
59 and 61 are consecutive primes, and 59+2*61 = 181 is prime. Hence 59 is in the sequence.
		

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(1200) | IsPrime(p+2*NextPrime(p))]; // Klaus Brockhaus, Dec 06 2010
  • Mathematica
    p = 3; Reap[Do[q = NextPrime[p]; If[PrimeQ[p + 2 q], Sow[p]]; p = q, {10^3}]][[2, 1]] (* Zak Seidov, Oct 14 2012 *)

A094104 Primes of the form 2*prime(n) + prime(n+1).

Original entry on oeis.org

7, 11, 17, 43, 53, 61, 89, 179, 241, 313, 331, 353, 449, 593, 673, 683, 691, 719, 733, 809, 859, 1021, 1051, 1237, 1259, 1321, 1481, 1709, 1741, 1933, 1979, 2083, 2111, 2137, 2221, 2237, 2311, 2333, 2371, 2473, 2531, 2741, 2767, 2957, 3163, 3469, 3643
Offset: 1

Views

Author

Giovanni Teofilatto, May 02 2004

Keywords

Comments

No intersection with A094105 (Primes of the form prime(m) + 2*prime(m+1)). In general, an integer of the form 2*prime(m) + prime(m+1) cannot be of the form prime(n) + 2*prime(n+1). - Zak Seidov, May 03 2014

Examples

			a(7) = 2*29 + 31 = 89.
		

Crossrefs

Cf. A094105.

Programs

  • Mathematica
    f[n_] := (2Prime[n] + Prime[n + 1]); f[ # ] & /@ Select[Range[160], PrimeQ[f[ # ]] &] (* Robert G. Wilson v *)
    Select[2#[[1]]+#[[2]]&/@Partition[Prime[Range[300]],2,1],PrimeQ] (* Harvey P. Dale, Jul 19 2022 *)
  • PARI
    q=2;forprime(p=3,1300,if(isprime(r=2*q+p),print1(r,","));q=p)

Extensions

Corrected and extended by Klaus Brockhaus and Robert G. Wilson v, May 07 2004

A241945 Indices n where both prime(n) + 2*prime(n+1) and 2*prime(n) + prime(n+1) are primes.

Original entry on oeis.org

2, 3, 6, 17, 27, 30, 48, 53, 57, 68, 94, 137, 138, 143, 156, 157, 248, 259, 269, 289, 296, 316, 360, 369, 402, 425, 429, 430, 432, 446, 474, 500, 522, 580, 596, 631, 656, 760, 777, 810, 828, 875, 906, 951, 994, 1154, 1163, 1233, 1273, 1338, 1346, 1352, 1378, 1381, 1385, 1391, 1402, 1422, 1436, 1495, 1552, 1602
Offset: 1

Views

Author

Zak Seidov, May 03 2014

Keywords

Examples

			n=2 is in the sequence because 3 + 2*5 = 13 and 5 + 2*3 = 11 are primes.
n=3 is in the sequence because 5 + 2*7 = 19 and 7 + 2*5 = 17 are primes.
n=6 is in the sequence because 17 + 2*13 = 43 and 13 + 2*17 = 47 are primes.
		

Crossrefs

Cf. A094104 (primes of form 2*p + q), A094105 (primes of form p + 2*q).

Programs

  • PARI
    isok(n) = my(p=prime(n), q=nextprime(p+1)); isprime(p+2*q) && isprime(2*p+q); \\ Michel Marcus, Jan 06 2019

A215808 Primes of the form 2*prime(k) - prime(k+1).

Original entry on oeis.org

3, 3, 17, 41, 47, 67, 151, 167, 199, 227, 251, 257, 347, 367, 557, 587, 601, 607, 641, 647, 727, 941, 971, 1051, 1091, 1097, 1117, 1181, 1217, 1277, 1361, 1427, 1447, 1447, 1487, 1487, 1499, 1607, 1697, 1741, 1747, 1741, 1777, 1877, 1901, 2087, 2143, 2281
Offset: 1

Views

Author

Zak Seidov, Sep 06 2012

Keywords

Comments

Corresponding values of k: 3, 4, 9, 15, 16, 21, 37, 40, 47, 51, 55, 56, 71, 74, 103 (A216075).

Examples

			k=3: 2*5-7=3, k=4: 2*7-11=3, k=9: 2*23-29=17.
		

Crossrefs

Programs

  • Mathematica
    pr=Prime[Range[1000]]; s=Select[2*Most[pr]-Rest[pr],PrimeQ]
    Select[2#[[1]]-#[[2]]&/@Partition[Prime[Range[500]],2,1],PrimeQ] (* Harvey P. Dale, Feb 25 2017 *)

A364411 a(n) = prime(n) + 2*prime(n+1).

Original entry on oeis.org

8, 13, 19, 29, 37, 47, 55, 65, 81, 91, 105, 119, 127, 137, 153, 171, 181, 195, 209, 217, 231, 245, 261, 283, 299, 307, 317, 325, 335, 367, 389, 405, 415, 437, 451, 465, 483, 497, 513, 531, 541, 563, 577, 587, 595, 621, 657, 677, 685, 695, 711, 721, 743, 765, 783
Offset: 1

Views

Author

Paul Curtz, Jul 23 2023

Keywords

Comments

All terms > 8 are odd.

Crossrefs

Cf. A000040, A001043, A062234, A094105, A100484, A191472 (first differences), A210497.

Programs

  • Mathematica
    ListConvolve[{2,1},Prime[Range[100]]] (* Paolo Xausa, Nov 02 2023 *)

Formula

a(n) = a(n-1) + A191472(n-1).
a(n) = A000040(n) + A100484(n+1).
a(n) = A000040(n+1) + A001043(n).
Showing 1-5 of 5 results.