vanEcksequences.py

import numpy as np
import matplotlib.pylab as plt
plt.close('all')

def vanEck(n):
    #starts at 0
    vanEck = np.array([0])
    #first value is 0
    i=vanEck[0]
    while i < n:
        last = vanEck[-1]
        pos = np.where(vanEck == last)
    #    print(i, last, pos[0])
        
        if pos[0].size == 1:
    #        print('if', 0, last)
            vanEck = np.append(vanEck, 0)
        else: 
    #        print('else', pos[0][-1], last)
            vanEck = np.append(vanEck, pos[0][-1] - pos[0][-2])
        i = vanEck[-1]
    
    x = np.linspace(0, n, n+1)
    plt.figure
    plt.plot(x, 'r--')
    plt.plot(vanEck)
    return vanEck

def negVanEck(n):
    vanEck = np.array([0])
    #first value is 0
    i=vanEck[0]
    while i < n:
        last = vanEck[-1]
        pos = np.where(vanEck == last)
        
        if pos[0].size == 1:
            vanEck1 = np.append(vanEck, -last)
        else: 
            vanEck1 = np.append(vanEck, pos[0][-1] - pos[0][-2])
        i = vanEck[-1]
    return vanEck

    x = np.linspace(0, n, n+1)
    plt.figure()
    plt.plot(x, 'r--')
    plt.plot(vanEck1)
    return vanEck