The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A287297 Fermat pseudoprimes n such that n+1 is prime. 2
 161038, 9115426, 143742226, 665387746, 1105826338, 3434672242, 11675882626, 16732427362, 18411253246, 81473324626, 85898088046, 98730252226, 134744844466, 136767694402, 161097973246, 183689075122, 315554044786, 553588254766, 778581406786, 1077392692846 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Kazimierz Szymiczek asked about the existence of such pseudoprimes in 1972 (Problem 42 in Rotkiewicz's book). Rotkiewicz found the first 6 terms. Rotkiewicz also proved that there is no Fermat pseudoprime n such that n-1 is prime. Subsequence of A006935. REFERENCES Andrzej Rotkiewicz, Pseudoprime Numbers and Their Generalizations, Student Association of the Faculty of Sciences, University of Novi Sad, Novi Sad, Yugoslavia, 1972. LINKS Amiram Eldar, Table of n, a(n) for n = 1..165 Andrzej Rotkiewicz,  On pseudoprimes having special forms and a solution of K. Szymiczek's problem, Acta Mathematica Universitatis Ostraviensis, Vol. 13, No. 1 (2005), pp. 57-71. EXAMPLE 161038 is in the sequence since it is a Fermat pseudoprime (2^161038 == 2 (mod 161038)), and 161038 + 1 = 161039 is prime. CROSSREFS Cf. A001567, A006935, A057942. Sequence in context: A236977 A108162 A270973 * A296117 A038681 A339676 Adjacent sequences: A287294 A287295 A287296 * A287298 A287299 A287300 KEYWORD nonn AUTHOR Amiram Eldar, May 26 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 7 15:43 EST 2023. Contains 360127 sequences. (Running on oeis4.)