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A275124 Multiples of 5 where Pisano periods of Fibonacci numbers A001175 and Lucas numbers A106291 agree.

%I A275124 #30 Jan 05 2025 19:51:40
%S A275124 55,110,155,165,205,220,305,310,330,355,385,410,440,465,495,505,605,
%T A275124 610,615,620,655,660,710,715,755,770,820,880,905,915,930,935,955,990,
%U A275124 1010,1045,1065,1085,1155,1205,1210,1220,1230,1240,1255,1265,1310,1320,1355,1395,1420,1430,1435,1485,1510,1515,1540,1555,1595,1640,1655,1705,1760,1810,1815,1830
%N A275124 Multiples of 5 where Pisano periods of Fibonacci numbers A001175 and Lucas numbers A106291 agree.
%C A275124 Multiples of 5 where A001175 and A106291 agree. See 1st comment of A106291.
%H A275124 Patrick Flanagan, Marc S. Renault, and Josh Updike, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Papers1/53-1/FlanaganRenaultUpdike06032014.pdf">Symmetries of Fibonacci Points, Mod m</a>, Fibonacci Quart. 53 (2015), no. 1, 34-41. See p. 7. (Is this the same sequence?)
%e A275124 55 is the first multiple of 5 where the Pisano period (Fibonacci) of n = 55 and the Pisano period (Lucas) of n = 55 agree (this is in this case 20).
%o A275124 (JavaScript)
%o A275124 let bases = [],
%o A275124     basesd = [],
%o A275124     baselimit = 2000;
%o A275124 for (let base = 2; base <= baselimit; base++) {
%o A275124     let fibs = [1 % base,1 % base],
%o A275124         lucas = [2 % base,1 % base],
%o A275124         repeatingf = false,
%o A275124         repeatingl = false;
%o A275124     while (!repeatingf) {
%o A275124         fibs.push((fibs[fibs.length - 2] + fibs[fibs.length - 1]) % base);
%o A275124         if (1 == fibs[fibs.length - 2] &&
%o A275124             0 == fibs[fibs.length - 1])
%o A275124             repeatingf = true;
%o A275124     }
%o A275124     while (!repeatingl) {
%o A275124         lucas.push((lucas[lucas.length - 2] + lucas[lucas.length - 1]) % base);
%o A275124         if ((lucas[0] == (lucas[lucas.length - 2] + lucas[lucas.length - 1]) % base) &&
%o A275124             (lucas[1] == (lucas[lucas.length - 2] + 2 *lucas[lucas.length - 1]) % base))
%o A275124             repeatingl = true;
%o A275124     }
%o A275124     if (fibs.length != lucas.length)
%o A275124         bases.push(base);
%o A275124 }
%o A275124 for (let i = 1; i <= baselimit/5; i++) {
%o A275124     if (!bases.includes(i * 5)) basesd.push(i * 5);
%o A275124 }
%o A275124 console.log(basesd.join(','));
%Y A275124 Cf. A001175, A106291.
%K A275124 nonn
%O A275124 1,1
%A A275124 _Dan Dart_, Jul 18 2016