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 A101690 #12 Nov 09 2020 03:23:40
%S A101690 1,4,2,9,7,1,5,9,2,2,6,8,9,2,0,4,2,0,0,2,7,7,2,3,0,6,9,2,6,2,7,1,6,5,
%T A101690 5,3,7,4,9,6,9,4,6,7,9,9,5,8,4,5,8,1,6,6,3,6,4,2,9,7,7,4,7,1,0,4,3,4,
%U A101690 6,5,8,2,4,7,4,3,5,8,9,0,0,1,7,2,0,7,8,9,1,8,1,9,1,3,3,1,6,6,4,0
%N A101690 Decimal expansion of the unique real number x whose Engel expansion is the Lucas sequence.
%F A101690 x = Sum_{n >= 1} 1/(Product_{1 <= i <= n} L(i)), where L(i) is the i-th Lucas number.
%e A101690 x = 1.4297159226892042002772306926271655374969467995845816636429774710...
%t A101690 Lucas[n_Integer?Positive] := Lucas[n] = Lucas[n-1] + Lucas[n-2]; Lucas[1] = 1; Lucas[2] = 3; N[Sum[1/Product[Lucas[i], {i, n}], {n, 500}], 100]
%t A101690 digits = 100; Clear[x]; x[m_] := x[m] = N[Sum[1/Product[LucasL[i], {i, 1, n}], {n, 1, m}], digits+5]; m = 10; While[x[m] != x[m-1], m++]; RealDigits[x[m], 10, digits][[1]] (* _Jean-François Alcover_, Nov 20 2015 *)
%Y A101690 Cf. A101689, A000204.
%K A101690 cons,nonn
%O A101690 1,2
%A A101690 _Ryan Propper_, Dec 11 2004
%E A101690 Offset corrected by _Amiram Eldar_, Nov 09 2020