A122506 - OEIS

%I #7 Aug 09 2024 22:05:43

%S 1,1,3,1,1,3,1,7,1,3,1,1,3,1,7,1,11,1,7,1,3,1,1,3,1,7,1,11,1,19,1,11,

%T 1,7,1,3,1,1,3,1,7,1,11,1,19,1,23,1,19,1,11,1,7,1,3,1

%N A symmetrical triangular array based on A018805 constructed by hand by adding ones between the primes and making the result symmetrical.

%C The first two terms past one come from removing the zeros from coefficients here: Expand[(x^2 - x - 1)*(x^2 + x - 1)] Abs[CoefficientList[1 - 3 x^2 + x^4, x]] {1, 0, 3, 0, 1} Expand[(x^3 - 2*x^2 - x + 1)*(x^3 - x^2 - 2*x + 1)] Abs[CoefficientList[1 - 3 x - x^2 + 7 x^3 - x^4 - 3 x^5 + x^6, x]] {1, 3, 1, 7, 1, 3, 1}

%e 1

%e 1, 3, 1

%e 1, 3, 1, 7, 1, 3, 1

%e 1, 3, 1, 7, 1, 11, 1, 7, 1, 3, 1

%e 1, 3, 1, 7, 1, 11, 1, 19, 1, 11, 1, 7, 1, 3, 1

%e 1, 3, 1, 7, 1, 11, 1, 19, 1, 23, 1, 19, 1, 11, 1, 7, 1, 3, 1

%Y Cf. A018805.

%K nonn,uned,tabl

%O 1,3

%A _Roger L. Bagula_, Sep 15 2006