OFFSET
1,1
COMMENTS
Composite k == 3 (mod 4) such that 2*(-4)^((k-3)/4) == -1 (mod k). - Robert Israel, Mar 21 2016
2*(-4)^((p-3)/4) == -1 (mod p) is satisfied by all primes p == 3 (mod 4), see A318908. - Jianing Song, Sep 05 2018
Numbers in A047713 that are congruent to 3 mod 4. Most terms are congruent to 7 mod 8. For terms congruent to 3 mod 8, see A244628. - Jianing Song, Sep 05 2018
Question: Is this a subsequence of A001262? I have verified that it contains all terms up to 2^64. - Joseph M. Shunia, Jul 02 2019
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..111 from Jianing Song using data from A047713)
MAPLE
select(t -> not isprime(t) and 1 + 2*(-4) &^ ((t-3)/4) mod t = 0, [seq(i, i=7..10^7, 4)]); # Robert Israel, Mar 21 2016
MATHEMATICA
Select[3 + 4*Range[10000000], PrimeQ[#] == False && PowerMod[1 + I, #, #] == Mod[1 - I, #] &]
PROG
(PARI) forstep(n=3, 10^7, 4, if(Mod(2, n)^((n-1)/2)==kronecker(2, n) && !isprime(n), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Mar 21 2016
STATUS
approved