

A122506


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


0



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
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OFFSET

1,3


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}


LINKS

Table of n, a(n) for n=1..56.


FORMULA

none available at this time


EXAMPLE

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


MATHEMATICA

a0 = {{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}} Flatten[a0]


CROSSREFS

Cf. A018805.
Sequence in context: A082465 A226856 A131327 * A010274 A137728 A054398
Adjacent sequences: A122503 A122504 A122505 * A122507 A122508 A122509


KEYWORD

nonn,uned,tabl


AUTHOR

Roger L. Bagula, Sep 15 2006


STATUS

approved



