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 A118428 #35 Feb 16 2025 08:33:01
%S A118428 1,9,9,1,9,6,4,1,9,6,6,0,5,0,3,5,0,2,1,0,9,7,7,4,1,7,5,4,5,8,4,3,7,4,
%T A118428 9,6,3,4,7,9,3,1,8,9,6,0,0,5,3,1,5,7,9,9,5,2,4,4,7,8,2,1,5,3,4,0,0,9,
%U A118428 5,1,9,8,0,3,0,9,6,2,2,1,8,3,5,6,3,1,4,1,5,7,7,0,2,2,7,1,9,0,1,7,0,9,9,1,6
%N A118428 Decimal expansion of heptanacci constant.
%C A118428 Other roots of the equation x^7 - x^6 - ... - x - 1 see in A239566. For n>=7, round(c^prime(n)) == 1 (mod 2*prime(n)). Proof in Shevelev link. - _Vladimir Shevelev_, Mar 21 2014
%C A118428 Note that we have: c + c^(-7) = 2, and the k-nacci constant approaches 2 when k approaches infinity (Martin Gardner). - _Bernard Schott_, May 07 2022
%D A118428 Martin Gardner, The Second Scientific American Book Of Mathematical Puzzles and Diversions, "Phi: The Golden Ratio", Chapter 8, p. 101, Simon & Schuster, NY, 1961.
%H A118428 S. Litsyn and Vladimir Shevelev, <a href="http://dx.doi.org/10.1142/S1793042105000339">Irrational Factors Satisfying the Little Fermat Theorem</a>, International Journal of Number Theory, vol.1, no.4 (2005), 499-512.
%H A118428 Vladimir Shevelev, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2014-March/012750.html">A property of n-bonacci constant</a>, Seqfan (Mar 23 2014)
%H A118428 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HeptanacciNumber.html">Heptanacci Number</a>
%H A118428 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HeptanacciConstant.html">Heptanacci Constant</a>
%H A118428 <a href="/index/Al#algebraic_07">Index entries for algebraic numbers, degree 7</a>.
%e A118428 1.9919641966050350210...
%t A118428 RealDigits[x/.FindRoot[x^7+Total[-x^Range[0,6]]==0,{x,2}, WorkingPrecision-> 110]][[1]] (* _Harvey P. Dale_, Dec 13 2011 *)
%o A118428 (PARI) polrootsreal(x^7 - x^6 - x^5 - x^4 - x^3 - x^2 - x - 1)[1] \\ _Charles R Greathouse IV_, Feb 11 2025
%Y A118428 Cf. A066178, A239566.
%Y A118428 k-nacci constants: A001622 (Fibonacci), A058265 (tribonacci), A086088 (tetranacci), A103814 (pentanacci), A118427 (hexanacci), this sequence (heptanacci).
%K A118428 nonn,cons
%O A118428 1,2
%A A118428 _Eric W. Weisstein_, Apr 27 2006