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 A106275 #25 Feb 16 2025 08:32:57
%S A106275 2,3,4,5,6,7,21,26,99,158,405
%N A106275 Numbers k for which the absolute value of the discriminant of the polynomial x^k - x^(k-1) - ... - x - 1 is a prime times 2^m for some m >= 0.
%C A106275 This polynomial is the characteristic polynomial of the Fibonacci and Lucas k-step recursions. Are the k-step recursions different -- in some way -- for the values of k that yield a prime*2^m discriminant? No other k < 10000.
%H A106275 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Fibonaccin-StepNumber.html">Fibonacci n-Step Number</a>.
%o A106275 (PARI) f(n) = poldisc('x^n-sum(k=0, n-1, 'x^k)); \\ A106273
%o A106275 isok(k) = my(x=abs(f(k))); ispseudoprime(x) || ispseudoprime(x/2^valuation(x, 2)); \\ _Michel Marcus_, Mar 26 2024
%Y A106275 Cf. A106273 (discriminant of the polynomial x^n - x^(n-1) - ... - x - 1).
%K A106275 nonn,hard,more
%O A106275 1,1
%A A106275 _T. D. Noe_, May 02 2005