The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A252943 Number of Fermat pseudoprimes between 2^n and 2^(n+1) that are not Carmichael numbers. 1
 0, 0, 0, 0, 0, 0, 0, 1, 1, 3, 3, 5, 10, 12, 14, 21, 31, 41, 64, 100, 127 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,10 COMMENTS This is a count, by power-of-two intervals, of the number of Fermat pseudoprimes that are not Carmichael numbers. A182490 contains the count of Carmichael numbers by power-of-two intervals. LINKS PROG (MAGMA) // Fermat pseudoprimes that are not Carmichael numbers, // count by power of two intervals for i:= 1 to 20 do   isum:=0;   for n:= 2^i + 1 to 2^(i+1) - 1 by 2 do      if (IsOne(2^(n-1) mod n)            and not IsPrime(n)            and not n mod CarmichaelLambda(n) eq 1)            then isum:=isum+1;      end if;   end for;   i, isum; end for; CROSSREFS Cf. A001567, A182490, A001567. Sequence in context: A132775 A174102 A217521 * A294617 A320450 A100886 Adjacent sequences:  A252940 A252941 A252942 * A252944 A252945 A252946 KEYWORD nonn,more AUTHOR Brad Clardy, Dec 25 2014 EXTENSIONS a(21) from Jon E. Schoenfield, Dec 25 2014 STATUS approved

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

Last modified January 27 08:31 EST 2020. Contains 331293 sequences. (Running on oeis4.)