A228353 -id:A228353 - cp's OEIS frontend

A258261 Primes p such that 3p - 4 is also prime.

2, 3, 5, 7, 11, 17, 19, 29, 31, 37, 47, 59, 61, 67, 79, 89, 107, 131, 149, 151, 157, 191, 197, 199, 227, 229, 241, 271, 277, 281, 311, 317, 367, 389, 397, 409, 421, 431, 457, 479, 499, 509, 521, 541, 547, 557, 571, 617, 631, 659, 661, 677, 691, 701, 719

Offset: 1

Zak Seidov, May 24 2015

This sequence is interesting because of the comments in A258233: for n > 1, if 3 * prime(n) - 4 is prime then A258233(n) = 1 + A071704(n), otherwise A258233 (n) = A071704(n). - Zak Seidov, Jun 04 2015

Subsequence of primes of A228121. - Michel Marcus, May 30 2015

			3 * 2 - 4 = 2, 3 * 3 - 4 = 5, 3 * 5 - 4 = 11, 3 * 7 - 4 = 17, 3 * 11 - 4 = 29 are all prime, so 2, 3, 5, 7, 11 are all in the sequence.
3 * 13 - 4 = 35 = 5 * 7, so 13 is not in the sequence.

Cf. A023209 (3p + 4), A071704, A258233, A228353, A228121.

[p: p in PrimesUpTo(1000) | IsPrime(3*p-4)]; // Vincenzo Librandi, May 25 2015

Select[Prime[Range[200]], PrimeQ[3# - 4] &]

forprime(p=1,10^3,if(isprime(3*p-4),print1(p,", "))) \\ Derek Orr, May 27 2015

A015787 Numbers n such that phi(n) + 8 | sigma(n + 8), where phi = A000010 and sigma = A000203.

Original entry on oeis.org

2, 18, 22, 34, 46, 48, 58, 94, 106, 132, 150, 166, 178, 180, 187, 214, 274, 346, 358, 394, 448, 466, 488, 526, 550, 562, 616, 624, 634, 660, 664, 744, 756, 772, 778, 782, 790, 798, 884, 886, 898, 934, 1138, 1174, 1186, 1354, 1366, 1438, 1618

Offset: 1

Robert G. Wilson v

nonn

From Robert Israel, Jul 23 2020: (Start)
The first odd terms are 187, 2407, 98587, 388315.
If p > 5 is in A228353 then 2*p is in the sequence. (End)

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

Cf. A000010, A000203, A228353.

select(t -> numtheory:-sigma(t+8) mod (numtheory:-phi(t)+8)=0, [$1..2000]); # Robert Israel, Jul 23 2020

is(n)=!(sigma(n+8)%(eulerphi(n)+8)) \\ Charles R Greathouse IV, Sep 25 2012

Corrected by Charles R Greathouse IV, Sep 25 2012

cp's OEIS Frontend

A258261 Primes p such that 3p - 4 is also prime.

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