A380246 Elimination order of the first person in a variation of the Josephus problem, where the number of skipped people correspond to the number of letters in consecutive numbers, called SpellUnder-Down.

1, 2, 1, 2, 5, 4, 2, 5, 6, 4, 6, 10, 3, 12, 6, 8, 15, 4, 13, 19, 14, 17, 5, 22, 18, 26, 6, 20, 13, 17, 19, 23, 7, 25, 21, 31, 22, 32, 8, 31, 38, 20, 29, 9, 27, 18, 43, 10, 15, 50, 37, 20, 16, 41, 11, 21, 39, 36, 34, 32, 29, 12, 36, 50, 27, 53, 35, 19, 45, 67, 13, 20, 70, 59, 74, 26, 21, 40, 65, 14, 49, 82, 33, 43, 28, 34, 53, 15

Offset: 1

Author

Tanya Khovanova and the MIT PRIMES STEP junior group, Jan 17 2025

Keywords

• nonn
• word

Comments

Arrange n people numbered 1,2,3,...,n in a circle, increasing clockwise. Starting with the person numbered 1, spell the letters of O-N-E, moving one person clockwise for each letter. Once you are done, eliminate the next person. Then, spell the letters of T-W-O; in other words, skip three people and eliminate the next person. Following this, spell the letters of T-H-R-E-E; in other words, skip five people and eliminate the next person. Continue until one person remains. a(n) is the order of elimination of the first person.

Examples

			Consider n = 4 people. The first person eliminated is number 4. This leaves the remaining people in order 1, 2, 3. The second person eliminated is number 1. Thus, person number 1 is eliminated in the second round, implying that a(4) = 2.
		

Crossrefs

Cf. A005589, A006257, A225381, A321298, A378635, A380201, A380202, A380204, A380246, A380247, A380248.

Programs

Python

from num2words import num2words as n2w
def spell(n):
    return sum(1 for c in n2w(n).replace(" and", "").replace(" ", "").replace(chr(44), "").replace("-", ""))
def nthRow(n):
    l = []
    for i in range(0,n):
        l.append(0)
    zp = 0
    for j in range(1,n+1):
        zc = 0
        while zc <= spell(j):
            if l[zp] == 0:
                zc += 1
            zp += 1
            zp = zp % n
        l[zp-1] = str(j)
    return l
l = []
for i in range(1,89):
    l += [nthRow(i)[0]]
print(l)

Python

from num2words import num2words as n2w
def f(n): return sum(1 for c in n2w(n).replace(" and", "") if c.isalpha())
def a(n):
    c, i, J = 1, 0, list(range(1, n+1))
    while len(J) > 0:
        i = (i + f(c))%len(J)
        q = J.pop(i)
        if q == 1: return c
        c = c+1
print([a(n) for n in range(1, 89)]) # Michael S. Branicky, Feb 15 2025