A005845 -id:A005845 - cp's OEIS frontend

A227905 Numbers of the form 4k+3 (A004767) that are Lucas pseudoprimes and Fermat pseudoprimes to base 2 (intersection of A005845 and A001567).

741751, 1024651, 5481451, 31150351, 109437751, 139952671, 178482151, 284301751, 383425351, 395044651, 407282851, 417027451, 498706651, 582799951, 612816751, 620072251, 652969351, 738820351, 977755351, 1126587151, 1204176751, 1397357851, 1588247851, 1789167931

Offset: 1

José María Grau Ribas, Oct 12 2013

nonn

This sequence uses the Bruckman definition of "Lucas pseudoprime". There are 400,114 examples less than 2^64. - Dana Jacobsen, Jan 07 2015

Amiram Eldar, Table of n, a(n) for n = 1..10000
J. M. Grau, A. M. Oller-Marcen, M. Rodríguez, D. Sadornil, Fermat test with gaussian base and Gaussian pseudoprimes, arXiv preprint arXiv:1401.4708 [math.NT], 2014.
W. Galway, Tables of pseudoprimes and related data [Includes a file with base-2 Fermat pseudoprimes up to 2^64.]

Cf. A004767 (4n+3).

Cf. A001567 (Fermat pseudoprimes to base 2), A005845 (Lucas pseudoprimes).

Select[4*Range[8000000]+3, CompositeQ[#] && PowerMod[2, (# - 1), # ] == 1 && Divisible[LucasL[#]-1, #] &] (* Amiram Eldar, Jun 27 2019 *)

perl -Mntheory=:all -nE 'chomp; say if ($%4)==3 && (lucas_sequence($,1,-1,$))[1] == 1' psps-below-2-to-64.txt  # _Dana Jacobsen, Jan 07 2015

perl -Mntheory=:all -E 'foroddcomposites { say if $%4 == 3 && ispseudoprime($,2) && (lucas_sequence($,1,-1,$))[1] == 1 } 1e14'  # Dana Jacobsen, Jan 10 2015

More terms from Dana Jacobsen, Jan 07 2015

a(16)-a(24) from Amiram Eldar, Jun 27 2019

A329240 Numbers that are both Fermat pseudoprimes to base 2 (A001567) and Bruckman-Lucas pseudoprimes (A005845).

Original entry on oeis.org

2465, 219781, 228241, 252601, 399001, 512461, 722261, 741751, 852841, 1024651, 1193221, 1533601, 1690501, 1735841, 1857241, 1909001, 2100901, 2165801, 2531845, 2603381, 2704801, 2757241, 3568661, 3828001, 4504501, 5049001, 5148001, 5481451, 6189121, 6368689, 6840001

Offset: 1

Amiram Eldar, Nov 08 2019

nonn

Van der Poel calculated the 215 terms below 6*10^8.
Van Zijl published the terms between 10^7 and 10^8.
These numbers were named "Van der Poel numbers" by Herman J. A. Duparc (1918-2002).

R. F. van Zijl, De getallen van Van der Poel (in Dutch), Master's thesis, Afstudeerverslag TU Delft, 1968.

Amiram Eldar, Table of n, a(n) for n = 1..655 (terms below 10^10)
H. J. A. Duparc, Belevenissen met van der Poel, in Vooruitgang bit voor bit: Liber Amicorum ac Collegarum bij het afscheid van Prof. dr. ir. W.L. van der Poel, 26 oktober 1988, Delftse Universitaire Pers, 1988.
Erik Lieuwens, Fermat pseudo primes, Doctoral Thesis, Delft University of Technology, 1971, pp. 29-30.
Willem Louis van der Poel, Primality tests with higher order recurrent sequences, in Recursie in retrospectief; voordrachten ter gelegenheid van het veertigjarig doctorsjubileum van Prof. dr. H.J.A. Duparc, Delft University of Technology, 1994.

Cf. A001567, A005845.

Select[Range[10^6], CompositeQ[#] && PowerMod[2, # - 1, #] == 1 && Divisible[LucasL[#] - 1, #] &]

A001610 a(n) = a(n-1) + a(n-2) + 1, with a(0) = 0 and a(1) = 2.

Original entry on oeis.org

0, 2, 3, 6, 10, 17, 28, 46, 75, 122, 198, 321, 520, 842, 1363, 2206, 3570, 5777, 9348, 15126, 24475, 39602, 64078, 103681, 167760, 271442, 439203, 710646, 1149850, 1860497, 3010348, 4870846, 7881195, 12752042, 20633238, 33385281, 54018520

Offset: 0

N. J. A. Sloane

For prime p, p divides a(p-1). - T. D. Noe, Apr 11 2009 [This result follows immediately from the fact that A032190(n) = (1/n)*Sum_{d|n} a(d-1)*phi(n/d). - Petros Hadjicostas, Sep 11 2017]
Generalization. If a(0,x)=0, a(1,x)=2 and, for n>=2, a(n,x)=a(n-1,x)+x*a(n-2,x)+1, then we obtain a sequence of polynomials Q_n(x)=a(n,x) of degree floor((n-1)/2), such that p is prime iff all coefficients of Q_(p-1)(x) are multiple of p (sf. A174625). Thus a(n) is the sum of coefficients of Q_(n-1)(x). - Vladimir Shevelev, Apr 23 2010
Odd composite numbers n such that n divides a(n-1) are in A005845. - Zak Seidov, May 04 2010; comment edited by N. J. A. Sloane, Aug 10 2010
a(n) is the number of ways to modify a circular arrangement of n objects by swapping one or more adjacent pairs. E.g., for 1234, new arrangements are 2134, 2143, 1324, 4321, 1243, 4231 (taking 4 and 1 to be adjacent) and a(4) = 6. - Toby Gottfried, Aug 21 2011
For n>2, a(n) equals the number of Markov equivalence classes with skeleton the cycle on n+1 nodes.  See Theorem 2.1 in the article by A. Radhakrishnan et al. below. - Liam Solus, Aug 23 2018
From Gus Wiseman, Feb 12 2019: (Start)
For n > 0, also the number of nonempty subsets of {1, ..., n + 1} containing no two cyclically successive elements (cyclically successive means 1 succeeds n + 1). For example, the a(5) = 17 stable subsets are:
  {1}, {2}, {3}, {4}, {5}, {6},
  {1,3}, {1,4}, {1,5}, {2,4}, {2,5}, {2,6}, {3,5}, {3,6}, {4,6},
  {1,3,5}, {2,4,6}.
(End)
Also the rank of the n-Lucas cube graph. - Eric W. Weisstein, Aug 01 2023

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

T. D. Noe, Table of n, a(n) for n = 0..500
Daniel Birmajer, Juan B. Gil, Michael D. Weiner, Linear recurrence sequences with indices in arithmetic progression and their sums, arXiv:1505.06339 [math.NT], 2015.
Ning-Ning Cao and Feng-Zhen Zhao, Some Properties of Hyperfibonacci and Hyperlucas Numbers, J. Int. Seq. 13 (2010) # 10.8.8.
Ligia L. Cristea, Ivica Martinjak, and Igor Urbiha, Hyperfibonacci Sequences and Polytopic Numbers, Journal of Integer Sequences, Vol. 19, 2016, Issue 7, #16.7.6.
Taras Goy and Mark Shattuck, Toeplitz-Hessenberg determinant formulas for the sequence F_n-1, Online J. Anal. Comb. (2025) Vol. 19, Paper 1, 1-26.
Petros Hadjicostas, Cyclic Compositions of a Positive Integer with Parts Avoiding an Arithmetic Sequence, Journal of Integer Sequences, 19 (2016), Article 16.8.2.
Fumio Hazama, Spectra of graphs attached to the space of melodies, Discrete Math., 311 (2011), 2368-2383. See Table 2.1.
Dov Jarden, Recurring Sequences, Riveon Lematematika, Jerusalem, 1966. [Annotated scanned copy] See p. 96.
Kantaphon Kuhapatanakul, On the Sums of Reciprocal Generalized Fibonacci Numbers, J. Int. Seq. 16 (2013) #13.7.1.
Rui Liu and Feng-Zhen Zhao, On the Sums of Reciprocal Hyperfibonacci Numbers and Hyperlucas Numbers, Journal of Integer Sequences, Vol. 15 (2012), #12.4.5. - From _N. J. A. Sloane_, Oct 05 2012
Richard J. Mathar, Hardy-Littlewood constants embedded into infinite products over all positive integers, sequence a_{1,s}, arXiv:0903.2514 [math.NT], 2009-2011.
El-Mehdi Mehiri, Saad Mneimneh, and Hacène Belbachir, The Towers of Fibonacci, Lucas, Pell, and Jacobsthal, arXiv:2502.11045 [math.CO], 2025. See p. 12.
Natascha Neumärker, Realizability of Integer Sequences as Differences of Fixed Point Count Sequences, Journal of Integer Sequences 12 (2009) 09.4.5, Example 10.
Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
Simon Plouffe, 1031 Generating Functions, Appendix to Thesis, Montreal, 1992
Adityanarayanan Radhakrishnan, Liam Solus, and Caroline Uhler. Counting Markov equivalence classes for DAG models on trees, arXiv:1706.06091 [math.CO], 2017; Discrete Applied Mathematics 244 (2018): 170-185.
Vladimir Shevelev, On divisibility of C(n-i-1,i-1) by i, Int. J. of Number Theory, 3 (2007), no.1, 119-139. [_Vladimir Shevelev_, Apr 23 2010]
Eric Weisstein's World of Mathematics, Graph Rank
Eric Weisstein's World of Mathematics, Lucas Cube Graph
John W. Wrench, Jr., Evaluation of Artin's constant and the twin-prime constant, Math. Comp., 15 (1961), 396-398.
Li-Na Zheng, Rui Liu, and Feng-Zhen Zhao, On the Log-Concavity of the Hyperfibonacci Numbers and the Hyperlucas Numbers, Journal of Integer Sequences, Vol. 17 (2014), #14.1.4.
Index entries for linear recurrences with constant coefficients, signature (2,0,-1).

Cf. A000032 (first differences), A000071, A000126, A000204, A000296, A001644, A032190, A169985, A174625, A306357.

List([0..40], n-> Lucas(1,-1,n+1)[2] -1); # G. C. Greubel, Jul 12 2019

a001610 n = a001610_list !! n
a001610_list =
   0 : 2 : map (+ 1) (zipWith (+) a001610_list (tail a001610_list))
-- Reinhard Zumkeller, Aug 21 2011

I:=[0,2]; [n le 2 select I[n] else Self(n-1)+Self(n-2)+1: n in [1..40]]; // Vincenzo Librandi, Mar 20 2015

[Lucas(n+1) -1: n in [0..40]]; // G. C. Greubel, Jul 12 2019

t = {0, 2}; Do[AppendTo[t, t[[-1]] + t[[-2]] + 1], {n, 2, 40}]; t
RecurrenceTable[{a[n] == a[n - 1] +a[n - 2] +1, a[0] == 0, a[1] == 2}, a, {n, 0, 40}] (* Robert G. Wilson v, Apr 13 2013 *)
CoefficientList[Series[x (2 - x)/((1 - x - x^2) (1 - x)), {x, 0, 40}], x] (* Vincenzo Librandi, Mar 20 2015 *)
Table[Fibonacci[n] + Fibonacci[n + 2] - 1, {n, 0, 40}] (* Eric W. Weisstein, Feb 13 2018 *)
LinearRecurrence[{2, 0, -1}, {2, 3, 6}, 20] (* Eric W. Weisstein, Feb 13 2018 *)
Table[LucasL[n] - 1, {n, 20}] (* Eric W. Weisstein, Aug 01 2023 *)
LucasL[Range[20]] - 1 (* Eric W. Weisstein, Aug 01 2023 *)

a(n)=([0,1,0; 0,0,1; -1,0,2]^n*[0;2;3])[1,1] \\ Charles R Greathouse IV, Sep 08 2016

vector(40, n, f=fibonacci; f(n+1)+f(n-1)-1) \\ G. C. Greubel, Jul 12 2019

[lucas_number2(n+1,1,-1) -1 for n in (0..40)] # G. C. Greubel, Jul 12 2019

a(n) = A000204(n)-1 = A000032(n+1)-1 = A000071(n+1) + A000045(n).
G.f.: x*(2-x)/((1-x-x^2)*(1-x)) = (2*x-x^2)/(1-2*x+x^3). [Simon Plouffe in his 1992 dissertation]
a(n) = F(n) + F(n+2) - 1 where F(n) is the n-th Fibonacci number. - Zerinvary Lajos, Jan 31 2008
a(n) = A014217(n+1) - A000035(n+1). - Paul Curtz, Sep 21 2008
a(n) = Sum_{i=1..floor((n+1)/2)} ((n+1)/i)*C(n-i,i-1). In more general case of polynomials Q_n(x)=a(n,x) (see our comment) we have Q_n(x) = Sum_{i=1..floor((n+1)/2)}((n+1)/i)*C(n-i,i-1)*x^(i-1). - Vladimir Shevelev, Apr 23 2010
a(n) = Sum_{k=0..n-1} Lucas(k), where Lucas(n) = A000032(n). - Gary Detlefs, Dec 07 2010
a(0)=0, a(1)=2, a(2)=3; for n>=3, a(n) = 2*a(n-1) - a(n-3). - George F. Johnson, Jan 28 2013
For n > 1, a(n) = A048162(n+1) + 3. - Toby Gottfried, Apr 13 2013
For n > 0, a(n) = A169985(n + 1) - 1. - Gus Wiseman, Feb 12 2019

A094395 Odd composite n such that n divides Fibonacci(n) + 1.

Original entry on oeis.org

5777, 10877, 17261, 75077, 80189, 100127, 113573, 120581, 161027, 162133, 163059, 231703, 300847, 430127, 618449, 635627, 667589, 851927, 1033997, 1106327, 1256293, 1388903, 1697183, 1842581, 2263127, 2435423, 2512889, 2662277

Offset: 1

Eric Rowland, May 01 2004

nonn

For each prime p, Fibonacci(p) = 5^((p-1)/2) mod p, so p divides Fibonacci(p) + 1 for each prime p=10k+-3. Hence it is interesting to seek also nonprimes with the same property, a motivation for this sequence. - Robert FERREOL, Jul 14 2015
Are all terms squarefree? A counterexample can't be divisible by the square of a prime < 1000. - Robert Israel, Jul 17 2015
Any term that is not squarefree must be divisible by the square of a Fibonacci-Wieferich prime (see the StackExchange link). There are believed to be infinitely many such primes, but none are known, and none are less than 2*10^14. - Robert Israel, Jul 22 2015

Giovanni Resta, Table of n, a(n) for n = 1..579 (terms < 4*10^9)
R. Israel and N. Elkies, Fibonacci == -1 mod p^2, Mathematics StackExchange, July 2015.
R. J. McIntosh and E. L. Roettger, A search for Fibonacci-Wieferich and Wolstenholme primes, Math. Comp. 76 (2007), 2087-2094.

Cf. A005845, A094394.

with(combinat):test:=n->(fibonacci(n)+1) mod n= 0:
select(test and not isprime ,[seq(2*k+1,k=1..10000)]);
# Robert FERREOL, Jul 14 2015

Select[ Range[3, 300000, 2], !PrimeQ[ # ] && Mod[Fibonacci[ # ] + 1, # ] == 0 &]

main(size)=my(v=vector(size),i,t=1); for(i=1,size, while(1, if(t%2==1&&omega(t)>1&&(fibonacci(t)+1)%t==0, v[i]=t; break, t++)); t++); v; \\ Anders Hellström, Jul 17 2015

is(n)=((Mod([1,1;1,0],n))^n)[1,2]==-1 && n%2 && !isprime(n) \\ Charles R Greathouse IV, Jul 20 2015

a(6)-a(14) from Robert G. Wilson v, May 01 2004

More terms from Ryan Propper, Aug 03 2005

A335669 Odd composite integers m such that A006497(m) == 3 (mod m).

Original entry on oeis.org

33, 65, 119, 273, 377, 385, 533, 561, 649, 1105, 1189, 1441, 2065, 2289, 2465, 2849, 4187, 4641, 6545, 6721, 11921, 12871, 13281, 14041, 15457, 16109, 18241, 19201, 22049, 23479, 24769, 25345, 28421, 30745, 31631, 34997, 38121, 38503, 41441, 45961, 46761, 48577

Offset: 1

Ovidiu Bagdasar, Jun 17 2020

nonn

If p is a prime, then A006497(p) == 3 (mod p).
This sequence contains the odd composite integers for which the congruence holds.
The generalized Pell-Lucas sequence of integer parameters (a,b) defined by V(n+2)=a*V(n+1)-b*V(n) and V(0)=2, V(1)=a, satisfy the identity V(p)==a (mod p) whenever p is prime and b=-1,1.
For a=3, b=-1, V(n) recovers the sequence A006497(n) (bronze Fibonacci numbers).

			33 is the first odd composite integer for which we have A006497(33) = 132742316047301964 == 3 (mod 33).

D. Andrica, O. Bagdasar, Recurrent Sequences: Key Results, Applications and Problems. Springer (to appear, 2020).

Amiram Eldar, Table of n, a(n) for n = 1..500
D. Andrica and O. Bagdasar, On some new arithmetic properties of the generalized Lucas sequences, preprint for Mediterr. J. Math. 18, 47 (2021).

Cf. A006497, A005845 (a=1), A330276 (a=2), A335670 (a=4), A335671 (a=5).

Select[Range[3, 50000, 2], CompositeQ[#] && Divisible[LucasL[#, 3] - 3, #] &] (* Amiram Eldar, Jun 18 2020 *)

is(m) = m%2 && !isprime(m) && [2, 3]*([0, 1; 1, 3]^m)[, 1]%m==3; \\ Jinyuan Wang, Jun 17 2020

More terms from Jinyuan Wang, Jun 17 2020

A141137 Even Fibonacci pseudoprimes: even composite numbers k such that either (1) k divides Fibonacci(k-1) if k mod 5 = 1 or -1 or (2) k divides Fibonacci(k+1) if k mod 5 = 2 or -2.

Original entry on oeis.org

8539786, 12813274, 17340938, 33940178, 64132426, 89733106, 95173786, 187473826, 203211098, 234735586, 353686906, 799171066, 919831058, 1188287794, 1955272906, 2166139898, 2309861746, 2864860298, 3871638242, 5313594466, 5867301826

Offset: 1

T. D. Noe, Jun 09 2008

These even Fibonacci pseudoprimes (FPPs) were found by Kenny Richardson (kenyai(AT)yahoo.com). See A081264 for odd FPPs and references. Be aware that some authors use the term "Fibonacci pseudoprime" for pseudoprimes in Lucas sequences. For example, see A005845 for Lucas V(1,-1) pseudoprimes.

a(69) > 2.6 * 10^11. - Dana Jacobsen, May 25 2015

Dana Jacobsen, Table of n, a(n) for n = 1..68
Dorin Andrica and Ovidiu Bagdasar, Recurrent Sequences: Key Results, Applications, and Problems, Springer (2020), p. 88.
Dorin Andrica and Ovidiu Bagdasar, On Generalized Lucas Pseudoprimality of Level k, Mathematics (2021) Vol. 9, 838.

Cf. A081264.

use ntheory ":all"; for (3..1e10) { my $n = $<<1; $e = (0,-1,1,1,-1)[$n%5]; next unless $e; say $n unless (lucas_sequence($n, 1, -1, $n+$e))[0]; } # _Dana Jacobsen, May 25 2015

a(19) from Giovanni Resta, Jul 20 2013

a(20)-a(21) from Dana Jacobsen, May 25 2015

A212424 Frobenius pseudoprimes with respect to Fibonacci polynomial x^2 - x - 1.

Original entry on oeis.org

4181, 5777, 6721, 10877, 13201, 15251, 34561, 51841, 64079, 64681, 67861, 68251, 75077, 90061, 96049, 97921, 100127, 113573, 118441, 146611, 161027, 162133, 163081, 186961, 197209, 219781, 231703, 252601, 254321, 257761, 268801, 272611

Offset: 1

Max Alekseyev, May 16 2012

nonn

Grantham incorrectly claims that "the first Frobenius pseudoprime with respect to the Fibonacci polynomial x^2 - x - 1 is 5777". Crandall and Pomerance state that the first such Frobenius pseudoprime is actually 4181.
The Frobenius (1,-1) pseudoprimes are a subset of the odd Fibonacci pseudoprimes A081264. Among other ways, this can be seen by Theorem 3.6.6 of Crandall and Pomerance (2005) where the Frobenius criterion with respect to x^2 - Px + Q is an additional condition on an input which has passed the Lucas test for the same polynomial. - Dana Jacobsen, Aug 05 2015
Many other quadratics have a sparser set of pseudoprimes.  For example, while there are 98702 pseudoprimes below 10^13 with respect to the Fibonacci polynomial, there are only 3897 for x^2 - 3x - 5. - Dana Jacobsen, Aug 05 2015
This is the intersection of A049062 and (A081264 union A141137), that is, composite k coprime to 5 such that Fibonacci(k) == (k/5) (mod k) and that k divides Fibonacci(k-(k/5)), where (k/5) is the Legendre or Jacobi symbol. - Jianing Song, Sep 12 2018

R. Crandall, C. B. Pomerance. Prime Numbers: A Computational Perspective. Springer, 2nd ed., 2005.

Amiram Eldar, Table of n, a(n) for n = 1..10000 (from Dana Jacobsen's site, terms 1..653 from Max Alekseyev)
Dorin Andrica and Ovidiu Bagdasar, Recurrent Sequences: Key Results, Applications, and Problems, Springer (2020), p. 89.
Jon Grantham, Frobenius pseudoprimes, Mathematics of Computation 70 (234): 873-891, 2001. doi: 10.1090/S0025-5718-00-01197-2.
Dana Jacobsen, Pseudoprime Statistics, Tables, and Data (includes terms through 10^13)
A. Rotkiewicz, Lucas and Frobenius Pseudoprimes, Annales Mathematicae Silesiane, 17 (2003): 17-39.
Lawrence Somer, Lucas sequences {Uk} for which U2p and Up are pseudoprimes for almost all primes p, Fibonacci Quart. 44 (2006), no. 1, 7-12.
Eric W. Weisstein, Frobenius Pseudoprime, MathWorld.

Cf. A049062, A081264, A141137.
Cf. also A005845, A094063, A094395, A094411.
Terms congruent to 2 or 3 mod 5 are given in A212423.

{ isFP(n) = if(ispseudoprime(n),return(0)); t=Mod(x*Mod(1,n),(x^2-x-1)*Mod(1,n))^n; (kronecker(5,n)==-1 && t==1-x)||(kronecker(5,n)==1 && t==x) }

use ntheory ":all"; foroddcomposites { say if is_frobenius_pseudoprime($,1,-1) } 1e10; # _Dana Jacobsen, Aug 05 2015

A335670 Odd composite integers m such that A014448(m) == 4 (mod m).

Original entry on oeis.org

9, 85, 161, 341, 705, 897, 901, 1105, 1281, 1853, 2465, 2737, 3745, 4181, 4209, 4577, 5473, 5611, 5777, 6119, 6721, 9701, 9729, 10877, 11041, 12209, 12349, 13201, 13481, 14981, 15251, 16185, 16545, 16771, 19669, 20591, 20769, 20801, 21845, 23323, 24465, 25345

Offset: 1

Ovidiu Bagdasar, Jun 17 2020

nonn

If p is a prime, then A014448(p)==4 (mod p).
This sequence contains the odd composite integers for which the congruence holds.
The generalized Pell-Lucas sequence of integer parameters (a,b) defined by V(n+2)=a*V(n+1)-b*V(n) and V(0)=2, V(1)=a, satisfy the identity V(p)==a (mod p) whenever p is prime and b=-1,1.
For a=4, b=-1, V(n) recovers A014448(n) (even Lucas numbers).

			9 is the first odd composite integer for which A014448(9)=439204==4 (mod 9).

D. Andrica, O. Bagdasar, Recurrent Sequences: Key Results, Applications and Problems. Springer (to appear, 2020).

Chai Wah Wu, Table of n, a(n) for n = 1..1000
D. Andrica and O. Bagdasar, On some new arithmetic properties of the generalized Lucas sequences, preprint for Mediterr. J. Math. 18, 47 (2021).

Cf. A006497, A005845 (a=1), A330276 (a=2), A335669 (a=3), A335671 (a=5).

M:= <<4|1>,<1|0>>:
f:= proc(n) uses LinearAlgebra:-Modular;
local A;
A:= Mod(n,M,integer[8]);
A:= MatrixPower(n,A,n);
2*A[1,1] - 4*A[1,2] mod n;
end proc:
select(t -> f(t) = 4 and not isprime(t), [seq(i,i=3..10^5,2)]); # Robert Israel, Jun 19 2020

Select[Range[3, 25000, 2], CompositeQ[#] && Divisible[LucasL[3#] - 4, #] &] (* Amiram Eldar, Jun 18 2020 *)

More terms from Jinyuan Wang, Jun 17 2020

A094401 Composite n such that n divides both Fibonacci(n-1) and Fibonacci(n) - 1.

Original entry on oeis.org

2737, 4181, 6721, 13201, 15251, 34561, 51841, 64079, 64681, 67861, 68251, 90061, 96049, 97921, 118441, 146611, 163081, 179697, 186961, 194833, 197209, 219781, 252601, 254321, 257761, 268801, 272611, 283361, 302101, 303101, 327313, 330929

Offset: 1

Eric Rowland, May 01 2004

nonn

Composite n such that Q^(n-1) = I (mod n), where Q is the Fibonacci matrix {{1,1},{1,0}} and I is the identity matrix. The identity is also true for the primes congruent to 1 or 4 (mod 5), which is sequence A045468. The period of Q^k (mod n) is the same as the period of the Fibonacci numbers F(k) (mod n), A001175. Hence the terms in this sequence are the composite n such that A001175(n) divides n-1. [T. D. Noe, Jan 09 2009]

Giovanni Resta, Table of n, a(n) for n = 1..1000 (first 200 terms from T. D. Noe)
Eric Weisstein, MathWorld: Fibonacci Q-Matrix.

Cf. A005845, A069106, A094394, A094400.

Select[Range[2, 50000], ! PrimeQ[ # ] && Mod[Fibonacci[ # - 1], # ] == 0 && Mod[Lucas[ # ] - 1, # ] == 0 &]

More terms from Ryan Propper, Sep 24 2005

A217120 Lucas pseudoprimes.

Original entry on oeis.org

323, 377, 1159, 1829, 3827, 5459, 5777, 9071, 9179, 10877, 11419, 11663, 13919, 14839, 16109, 16211, 18407, 18971, 19043, 22499, 23407, 24569, 25199, 25877, 26069, 27323, 32759, 34943, 35207, 39059, 39203, 39689, 40309, 44099, 46979, 47879

Offset: 1

Robert Baillie, Mar 16 2013

nonn

Lucas pseudoprimes with parameters (P, Q) defined by Selfridge's Method A.

Amiram Eldar, Table of n, a(n) for n = 1..10000 (from Dana Jacobsen's site, terms 1..2998 from R. J. Mathar)
Martin R. Albrecht, Jake Massimo, Kenneth G. Paterson, and Juraj Somorovsky, Prime and Prejudice: Primality Testing Under Adversarial Conditions, Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security, 281-298.
Robert Baillie and Samuel S. Wagstaff, Jr., Lucas Pseudoprimes, Mathematics of Computation, 35 (1980), 1391-1417.
Robert Baillie, Mathematica program to generate terms
David Bernier, A strong primality test based on third-order linear recurrences, ResearchGate (2025). See p. 6.
Dana Jacobsen, Pseudoprime Statistics, Tables, and Data (includes terms through 10^14)

Cf. A005845 (Lucas pseudoprimes as defined by Bruckman).
Cf. A217255 (strong Lucas pseudoprimes as defined by Baillie and Wagstaff).
Cf. A217719 (extra strong Lucas pseudoprimes as defined by Baillie).

Mathematica
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cp's OEIS Frontend

A227905 Numbers of the form 4k+3 (A004767) that are Lucas pseudoprimes and Fermat pseudoprimes to base 2 (intersection of A005845 and A001567).

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A329240 Numbers that are both Fermat pseudoprimes to base 2 (A001567) and Bruckman-Lucas pseudoprimes (A005845).

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A001610 a(n) = a(n-1) + a(n-2) + 1, with a(0) = 0 and a(1) = 2.

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A094395 Odd composite n such that n divides Fibonacci(n) + 1.

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A335669 Odd composite integers m such that A006497(m) == 3 (mod m).

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A141137 Even Fibonacci pseudoprimes: even composite numbers k such that either (1) k divides Fibonacci(k-1) if k mod 5 = 1 or -1 or (2) k divides Fibonacci(k+1) if k mod 5 = 2 or -2.

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A212424 Frobenius pseudoprimes with respect to Fibonacci polynomial x^2 - x - 1.

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