The On-Line Encyclopedia of Integer Sequences (OEIS)

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A286715

Lesser of twin primes for which phi(p-1) < phi(p+1).
(history; published version)

#9 by Alois P. Heinz at Wed Sep 11 16:45:46 EDT 2019

STATUS

reviewed

approved

#8 by Michel Marcus at Wed Sep 11 15:05:05 EDT 2019

STATUS

proposed

reviewed

#7 by Amiram Eldar at Wed Sep 11 14:47:35 EDT 2019

STATUS

editing

proposed

#6 by Amiram Eldar at Wed Sep 11 13:09:16 EDT 2019

MATHEMATICA

s = {}; p = 3; Do[q = NextPrime[p]; If[q - p != 2, p = q; Continue[]]; If[EulerPhi[p + 1] > EulerPhi[p - 1], AppendTo[s, p]]; p = q, {15500}]; s (* Amiram Eldar, Sep 11 2019 *)

#5 by Amiram Eldar at Wed Sep 11 13:07:54 EDT 2019

LINKS

Amiram Eldar, <a href="/A286715/b286715.txt">Table of n, a(n) for n = 1..10000</a>

STATUS

approved

editing

#4 by N. J. A. Sloane at Sat May 13 17:19:26 EDT 2017

STATUS

proposed

approved

#3 by Michel Marcus at Sat May 13 12:36:37 EDT 2017

STATUS

editing

proposed

#2 by Michel Marcus at Sat May 13 12:35:33 EDT 2017

NAME

allocated Lesser of twin primes for Michel Marcuswhich phi(p-1) < phi(p+1).

DATA

3, 2381, 3851, 14561, 17291, 20021, 20231, 26951, 34511, 41231, 47741, 50051, 52361, 55931, 57191, 65171, 67211, 67271, 70841, 82811, 87011, 98561, 101501, 101531, 108461, 117041, 119771, 126491, 129221, 134681, 136991, 142871, 145601, 150221, 156941, 165551, 166601

OFFSET

1,1

LINKS

Stephan Ramon Garcia, Elvis Kahoro, Florian Luca, <a href="https://arxiv.org/abs/1705.02485">Primitive root discrepancy for twin primes</a>, arXiv:1705.02485 [math.NT], 2017.

PROG

(PARI) lista(nn) = forprime(p=2, nn, if (isprime(p+2) && (eulerphi(p-1) < eulerphi(p+1)), print1(p, ", ")));

CROSSREFS

Cf. A001359, A006512, A008330, A286714.

KEYWORD

allocated

nonn

AUTHOR

Michel Marcus, May 13 2017

STATUS

approved

editing

#1 by Michel Marcus at Sat May 13 12:27:37 EDT 2017

NAME

allocated for Michel Marcus

KEYWORD

allocated

STATUS

approved