

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
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OFFSET

1,10


COMMENTS

This is a count, by poweroftwo intervals, of the number of Fermat pseudoprimes that are not Carmichael numbers. A182490 contains the count of Carmichael numbers by poweroftwo intervals.


LINKS

Table of n, a(n) for n=1..21.


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^(n1) 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



