A152597 Where records occur in A001917.

2, 4, 11, 21, 31, 110, 124, 185, 279, 399, 716, 1028, 4552, 6207, 6543, 11424, 11557, 12251, 16199, 23043, 43390, 155798, 203095, 457523, 699782, 865318, 1294026, 2918851, 5635889, 6459777, 8999147, 9213126, 22383796, 28194383, 32131750, 105097565, 404165580

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..47

Formula

a(n) = A000720(A226216(n)). - Amiram Eldar, Nov 16 2023

Example

First few terms of A001917 (has offset 2) are 1, 1, 2, 1, 1, 2, 1, 2, 1, 6, so a(1) to a(3) are 2, 4, 11.

Prog

(Magma) W:=[]; r:=0; for n in [2..100000] do p:=NthPrime(n); a:=(p-1)/Modorder(2, p); if r lt a then r:=a; Append(~W, n); end if; end for; print W;
(Python)
from itertools import islice
from sympy import nextprime, n_order
def agen():
    record, v, p = -1, 1, 3
    while True:
        if v > record: record = v; yield record
        v, p = (p-1)//n_order(2, p), nextprime(p)
print(list(islice(agen(), 20))) # Michael S. Branicky, Oct 09 2022

Crossrefs

Cf. A001917 ((p-1)/x, where p = prime(n) and x = smallest positive integer such that 2^x == 1 mod p), A152598 (records in A001917), A000720, A226216.

Sequence in context: A278446 A349566 A026275 * A320679 A126972 A295947

Adjacent sequences: A152594 A152595 A152596 * A152598 A152599 A152600

Keyword

nonn

Author

Klaus Brockhaus, Dec 09 2008

Extensions

a(27)-a(37) from Amiram Eldar, Mar 08 2019

Status

approved