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A252943
Number of Fermat pseudoprimes to base 2 between 2^n and 2^(n+1) that are not Carmichael numbers.
2
0, 0, 0, 0, 0, 0, 0, 1, 1, 3, 3, 5, 10, 12, 14, 21, 31, 41, 64, 100, 127, 165, 216, 288, 397, 572, 723, 955, 1344, 1793, 2399, 3280, 4228, 5728, 7738, 10223, 13895, 18324, 24437, 33007, 43850, 58173, 77938, 104689, 139195, 187497, 252020, 337731, 452631, 606942
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
Jan Feitsma and William F. Galway, Tables of pseudoprimes and related data.
R. G. E. Pinch, Pseudoprimes up to 10^13.
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
KEYWORD
nonn
AUTHOR
Brad Clardy, Dec 25 2014
EXTENSIONS
a(21) from Jon E. Schoenfield, Dec 25 2014
a(22)-a(50) from Daniel Suteu, Mar 06 2023
STATUS
approved