A082433 a(n) = A072181(n) - p, where p is the largest prime < A072181(n) - 1.
3, 5, 7, 7, 11, 11, 11, 11, 13, 23, 17, 17, 17, 41, 191, 47, 31, 53, 53, 53, 31, 179, 61, 61, 337, 131, 523, 523, 419, 223, 223, 223, 223, 79, 3821, 3821, 3821, 23399, 21269, 21269, 3607
Offset: 3
Examples
a(4) = A072181(4)-7 = 12-7 = 5.
Programs
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Python
from sympy import factorint, isprime def afindn(terms): prev_factors, prevan, prevk, n = dict(), 1, None, 2 for n in range(2, terms+1): n_factors, an = factorint(n), 1 for pi in set(prev_factors.keys()) | set(n_factors.keys()): ei = prev_factors[pi] if pi in prev_factors else 1 fi = n_factors[pi] if pi in n_factors else 1 an *= pi**(ei*fi) if n >= 3: if an != prevan: k = 3 while not isprime(an - k): k += 2 else: k = prevk print(k, end=", ") prevk = k prev_factors, prevan = factorint(an), an afindn(36) # Michael S. Branicky, Sep 05 2021
Extensions
a(36)-a(40) from Jinyuan Wang, Sep 05 2020
a(41)-a(43) from Michael S. Branicky, Sep 05 2021
Comments