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

2, 23, 47, 59, 83, 89, 113, 167, 269, 389, 419, 509, 659, 839, 1049, 1259, 1889, 2099, 2309, 2729, 3359, 3989, 4289, 4409, 5879, 6089, 6719, 9029, 9239, 10289, 10709, 11549, 13649, 13859, 15329, 15959, 20789, 21839, 23099, 25409, 27299, 30029, 34649, 43889, 51869

Offset: 1

Author

Paul Muljadi, Sep 22 2005

Keywords

• nonn

Comments

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

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

Examples

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

Links

• Amiram Eldar, Table of n, a(n) for n = 1..115
• PrimeFan, Listing of Esoteric Integer Sequences, See RNTFS00013, RNTFS00014.
• PrimeFan, Esoteric Integer Sequences [Cached copy]

Crossrefs

Cf. A000040, A100827.

Extensions

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

More terms from T. D. Noe, Mar 16 2010

More terms from Amiram Eldar, Dec 24 2020