This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A090820 #35 Jan 26 2024 12:47:18 %S A090820 25,60,120,125,180,240,300,360,480,540,600,625,660,720,840,900,960, %T A090820 1080,1200,1320,1440,1500,1620,1680,1800,1860,1920,1980,2160,2400, %U A090820 2460,2520,2640,2700,2760,2880,3000,3060,3125,3240,3300,3360,3420,3600,3660,3720 %N A090820 Composite n such that Fibonacci(n) == Legendre(n,5) (mod n). %C A090820 If n is a prime, not 5, then Fibonacci(n) == Legendre(n,5) (mod n) (see for example G. H. Hardy and E. M. Wright, Theory of Numbers). %H A090820 Amiram Eldar, <a href="/A090820/b090820.txt">Table of n, a(n) for n = 1..10000</a> %H A090820 Masataka Yorinaga, <a href="http://ousar.lib.okayama-u.ac.jp/ja/journal/mjou/19/1/article/33418">On a congruencial property of Fibonacci numbers (numerical experiments)</a>, Math. J. Okayama Univ. 19 (1976/77), no. 1, 5-10. %H A090820 Masataka Yorinaga, <a href="http://ousar.lib.okayama-u.ac.jp/ja/journal/mjou/19/1/article/33420">On a congruencial property of Fibonacci numbers (considerations and remarks)</a>, Math. J. Okayama Univ. 19 (1976/77), no. 1, 11-17. %t A090820 Select[ Range[ 2, 5000 ], ! PrimeQ[ # ] && Mod[ Fibonacci[ # ] - JacobiSymbol[ #, 5 ], # ] == 0 & ] %o A090820 (PARI) N=10^4; for(n=2,N, if(Mod((fibonacci(n)), n)==kronecker(n,5) && !isprime(n), print1(n, ", "))); %Y A090820 Cf. A049062, A093372, A094063. %K A090820 nonn %O A090820 1,1 %A A090820 _Eric Rowland_, Apr 29 2004 %E A090820 More terms from _Felix Fröhlich_, Apr 24 2014