A122506 A symmetrical triangular array based on A018805 constructed by hand by adding ones between the primes and making the result symmetrical.

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, 1, 7, 1, 3, 1, 1, 3, 1, 7, 1, 11, 1, 19, 1, 23, 1, 19, 1, 11, 1, 7, 1, 3, 1

Offset: 1

Author

Roger L. Bagula, Sep 15 2006

Keywords

• nonn
• uned
• tabl

Comments

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}

Examples

			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, 1, 7, 1, 3, 1
1, 3, 1, 7, 1, 11, 1, 19, 1, 23, 1, 19, 1, 11, 1, 7, 1, 3, 1
		

Crossrefs

Cf. A018805.