Stefan Gog - cp's OEIS frontend

User: Stefan Gog

Stefan Gog has authored 2 sequences.

A329983 For any n > 0, define the sequence b(1) = n, b(i+1) = (b(i) * i) mod (b(i) + i); a(n) is the least i such that b(i) = 0, or -1 if 0 is never reached.

1, 13, 3, 85, 13, 85, 7, 58, 4, 13, 7, 85, 5, 7, 13, 58, 58, 85, 85, 13, 5, 85, 7, 291, 13, 85, 58, 85, 58, 7, 85, 291, 85, 85, 13, 58, 13, 58, 291, 11, 6, 58, 13, 7, 13, 85, 7, 291, 58, 85, 9, 85, 7, 13, 13, 58, 85, 13, 9, 58, 291, 291, 13, 11

Offset: 0

Stefan Gog, Nov 26 2019

nonn

Rémy Sigrist, Table of n, a(n) for n = 0..10000

Cf. A308651.

f(m, n) = (m*n) % (m+n);
a(n) = {my(i=1); while (n, n = f(n, i); i++;); i;} \\ Michel Marcus, Nov 28 2019

def k(a,b):
    return ((a*b)%(a+b))
numberList=[]
def repeat(a):
    i=1
    while a!=0:
        a= k(a,i)
        i=i+1
    numberList.append(i)
for x in range(10000):
    repeat(x)
print(numberList)

A308651 a(n+1) = k(a(n), n), where k(m, n) = (m*n) mod (m+n) and with a(1) = 5.

Original entry on oeis.org

5, 5, 3, 3, 5, 5, 8, 11, 12, 3, 4, 14, 12, 6, 4, 3, 10, 8, 14, 2, 18, 27, 6, 22, 22, 33, 32, 38, 8, 10, 20, 8, 16, 38, 68, 11, 20, 56, 60, 63, 48, 10, 4, 31, 14, 40, 34, 59, 50, 74, 104, 34, 48, 19, 4, 43, 32, 44, 2, 57, 27, 63, 31, 73, 14, 41, 31, 19, 74, 101, 59, 29, 68, 29, 86, 10, 72, 31, 20, 95, 75, 147, 146, 210, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset: 1

Stefan Gog, Aug 23 2019

a[1] = 5; a[n_] := a[n] = Mod[a[n - 1] * (n - 1), a[n - 1] + n - 1]; Array[a, 100] (* Amiram Eldar, Aug 29 2019 *)

def k(a,b):
    return (a*b)%(a+b)
a = [5]
for n in range(1, 100):
    a.append(k(a[-1], n))
print(a)

a(k) = 0 for k >= 85. - Jinyuan Wang, Aug 26 2019

5 is one of the first starting values that produces rather long sequence until collapses to zero.

cp's OEIS Frontend

User: Stefan Gog

A329983 For any n > 0, define the sequence b(1) = n, b(i+1) = (b(i) * i) mod (b(i) + i); a(n) is the least i such that b(i) = 0, or -1 if 0 is never reached.

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