(49g 50g) Zigzag numbers

10022018, 01:53 PM
(This post was last modified: 09222019 02:42 PM by John Keith.)
Post: #1




(49g 50g) Zigzag numbers
The following program returns a list of the Euler zigzag numbers (A000111) from 0 though n. The evenindexed terms (starting with 0) of the list are the unsigned Euler numbers, also known as secant numbers (A000364). The oddindexed terms (starting with 1) are the tangent numbers, A000182.
Code:
The next program returns rows 0 through n of A008281, the triangle from which the zigzag numbers are derived: Code:
These programs are based on the "Boustrophedon transform", which is detailed in the Links section of the A008281 link above. They requireGoferLists, and should be used in exact mode due to the size of integers involved. Edited 9/22/2019 to replace the first program with a smaller, faster version. 

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