OFFSET

1,2

COMMENTS

LINKS

M. Fleuren, Factoring of the Smarandache Mirror Sequence.

F. Smarandache, Only Problems, Not Solutions!, Mirror sequence, problem 19, page 20.

EXAMPLE

a(4) = 2 since 4321234 = 2 * 2160617;

a(6) = 3 since 65432123456 = 2^6 * 7 * 146053847.

PROG

(Python)

from sympy import primefactors

def A361624(n): return len(primefactors(int(''.join(map(str, range(n, 1, -1)))+''.join(map(str, range(1, n+1)))))) # Chai Wah Wu, Mar 21 2023

CROSSREFS

KEYWORD

nonn,base,more

AUTHOR

Bernard Schott, Mar 18 2023

EXTENSIONS

a(36)-a(54) from Amiram Eldar, Mar 19 2023

a(42) corrected by Sean A. Irvine, Sep 26 2023

a(55) from Sean A. Irvine, Oct 16 2023

STATUS

approved