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 A142248 #22 Aug 10 2025 11:55:01 %S A142248 1,3,7,11,17,29,47,75,123,199,321,521,843,1363,2207,3571,5777,9349, %T A142248 15127,24475,39603,64079,103681,167761,271443,439203,710647,1149851, %U A142248 1860497,3010349,4870847,7881195,12752043,20633239,33385281,54018521,87403803,141422323,228826127,370248451 %N A142248 Odd numbers in A138123. %F A142248 Conjectures from _Chai Wah Wu_, Apr 15 2024: (Start) %F A142248 a(n) = a(n-1) + a(n-2) + a(n-3) - a(n-4) - a(n-5) for n > 6. %F A142248 G.f.: x*(-2*x^5 - 3*x^4 + 3*x^2 + 2*x + 1)/((x - 1)*(x^2 + x - 1)*(x^2 + x + 1)). (End) %o A142248 (PARI) L(n) = fibonacci(n+1)+fibonacci(n-1); \\ A000204 %o A142248 T(n, k) = if (k<n, return(0)); if (n==k, return(L(n))); if (k==2*n, return((-1)^(n+1))); return(0); \\ A138123 %o A142248 lista(nn) = my(list = List()); for (k=1, nn, my(i=k, j=1, s=0); for (m=1, k, s += T(i,j); i--; j++;); if ((s>0) && (s%2), listput(list, s));); Set(list); %Y A142248 Cf. A000204, A138123. %K A142248 nonn %O A142248 1,2 %A A142248 _Paul Curtz_, Sep 18 2008 %E A142248 Edited by _N. J. A. Sloane_, Dec 10 2008 %E A142248 More terms from _Michel Marcus_, Apr 16 2024