login
A358275
Least prime factor of A098129(n).
1
2, 71, 2, 5, 2, 1141871, 2, 3, 2, 58728589, 2, 3, 2, 5, 2, 3, 2, 277, 2, 4643, 2, 29, 2, 5, 2, 3, 2, 37, 2, 3, 2, 13, 2, 3, 2, 264439098646852541, 2, 7, 2, 53, 2, 7, 2, 3, 2, 587, 2, 3, 2, 45307, 2, 3, 2, 5, 2, 11, 2, 7, 2, 13, 2, 3, 2, 5, 2, 3, 2, 17, 2, 3, 2, 983, 2, 5, 2, 53, 2, 11
OFFSET
2,1
FORMULA
a(n) = A020639(A098129(n)).
a(n) = 2 if n is even. - Chai Wah Wu, Apr 15 2023
EXAMPLE
a(3) = 71 because 71 is the smallest prime factor of A098129(3) = 122333.
a(7) = 1141871 because 1141871 is the smallest prime factor of A098129(7) = 1223334444555556666667777777.
PROG
(Python)
from sympy import primefactors
def A358275(n): return min(primefactors(int(''.join(str(j)*j for j in range(1, n+1))))) if n&1 else 2 # Chai Wah Wu, Apr 15 2023
CROSSREFS
Sequence in context: A151686 A201555 A348456 * A293753 A164554 A141908
KEYWORD
nonn
AUTHOR
David Cleaver, Mar 26 2023
STATUS
approved