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%I #6 Oct 24 2020 17:26:33
%S 4,8,10,20,40,44,104,136,152,170,190,232,260,286,442,580,740,836,890,
%T 1364,1378,1990,2204,2260,2584,2626,2684,2834,3016,3160,3230,3926,
%U 4220,4636,5662,6290,7208,7384,7540,7676,7964,8294,8420,9164,9316,9320,10070,11476
%N Even composites m such that A056854(m)==7 (mod m).
%C If p is a prime, then A056854(p)==7 (mod p).
%C This sequence contains the even composite integers for which the congruence holds.
%C The generalized Pell-Lucas sequence of integer parameters (a,b) defined by V(m+2)=a*V(m+1)-b*V(m) and V(0)=2, V(1)=a, satisfy the identity V(p)==a (mod p) whenever p is prime and b=-1,1.
%C For a=7 and b=1, V(m) recovers A056854(m).
%D D. Andrica, O. Bagdasar, Recurrent Sequences: Key Results, Applications and Problems. Springer (2020)
%D D. Andrica, O. Bagdasar, On some new arithmetic properties of the generalized Lucas sequences, Mediterr. J. Math. (to appear, 2021)
%t Select[Range[2, 20000, 2], CompositeQ[#] && Divisible[2*ChebyshevT[#, 7/2] - 7, #] &]
%Y Cf. A338082 (sequence of odd terms), A337777 (a=3), A338311 (a=6).
%K nonn
%O 1,1
%A _Ovidiu Bagdasar_, Oct 22 2020