login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A337629
Odd composite integers m such that U(m)^2 == 1 (mod m) and V(m) == 6 (mod m), where U(m) and V(m) are the m-th generalized Lucas and Pell-Lucas numbers of parameters a=6 and b=-1, respectively.
2
57, 481, 629, 721, 779, 1121, 1441, 1729, 2419, 2737, 6721, 7471, 8401, 9361, 10561, 11521, 11859, 12257, 15281, 16321, 16583, 18849, 24721, 25441, 25593, 33649, 35219, 36481, 36581, 37949, 39169, 41041, 45961, 46999, 50681, 52417, 53041, 53521, 54757, 55537
OFFSET
1,1
COMMENTS
For a,b integers, the following sequences are defined:
generalized Lucas sequences by U(n+2)=a*U(n+1)-b*U(n) and U(0)=0, U(1)=1,
generalized Pell-Lucas sequences by V(n+2)=a*V(n+1)-b*V(n) and V(0)=2, V(1)=a.
These satisfy the identities U(p)^2 == 1 and V(p)==a (mod p) for p prime and b=1,-1.
These numbers may be called weak generalized Lucas-Bruckner pseudoprimes of parameters a and b. The current sequence is defined for a=6 and b=-1.
LINKS
D. Andrica and O. Bagdasar, On some new arithmetic properties of the generalized Lucas sequences, preprint for Mediterr. J. Math. 18, 47 (2021).
MATHEMATICA
Select[Range[3, 15000, 2], CompositeQ[#] && Divisible[Fibonacci[#, 6]*Fibonacci[#, 6] - 1, #] && Divisible[LucasL[#, 6] - 6, #] &]
CROSSREFS
Cf. A337625 (a=1), A337626 (a=3), A337627 (a=4), A337628 (a=5).
Sequence in context: A076459 A268260 A184224 * A218812 A290779 A027143
KEYWORD
nonn
AUTHOR
Ovidiu Bagdasar, Sep 19 2020
EXTENSIONS
More terms from Amiram Eldar, Sep 19 2020
STATUS
approved