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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 (list; table; graph; refs; listen; history; text; internal format)
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

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Last modified June 24 17:49 EDT 2019. Contains 324328 sequences. (Running on oeis4.)