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A105440 Highly cototient numbers that are prime, or intersection of A000040 and A100827. 2

%I #34 Dec 24 2020 21:25:44

%S 2,23,47,59,83,89,113,167,269,389,419,509,659,839,1049,1259,1889,2099,

%T 2309,2729,3359,3989,4289,4409,5879,6089,6719,9029,9239,10289,10709,

%U 11549,13649,13859,15329,15959,20789,21839,23099,25409,27299,30029,34649,43889,51869

%N Highly cototient numbers that are prime, or intersection of A000040 and A100827.

%C 2 is definitely a "highly cototient prime". Oddly enough, though, PrimeFan does not list it as safe prime that is also a highly cototient number in RNTFS00013 even though he considers 1 to be a prime. - Robert Happelberg (roberthappelberg(AT)yahoo.com), Oct 04 2005

%C 115 of the first 229 terms (just over 50%) of A100827 are prime. - _Jud McCranie_, May 18 2017

%H Amiram Eldar, <a href="/A105440/b105440.txt">Table of n, a(n) for n = 1..115</a>

%H PrimeFan, <a href="http://primefan.tripod.com/EsotericIntegerSequences.html">Listing of Esoteric Integer Sequences</a>, See RNTFS00013, RNTFS00014.

%e 269 (after 59 & 89) is the first prime in a sequence of primes which are congruent to 9 mod 10.

%Y Cf. A000040, A100827.

%K nonn

%O 1,1

%A _Paul Muljadi_, Sep 22 2005

%E More terms from Robert Happelberg (roberthappelberg(AT)yahoo.com), Oct 04 2005

%E More terms from _T. D. Noe_, Mar 16 2010

%E More terms from _Amiram Eldar_, Dec 24 2020

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)