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%I #22 Mar 05 2020 03:24:57
%S 0,2,4,4,4,10,4,8,8,1,2,5,3,6,7,4,5,8,6,2,6,3,4,9,2,6,11,2,4,10,4,9,8,
%T 6,6,12,3,6,8,4,6,7,3,6
%N Number of prime factors, counted with multiplicity, of A173426(n) = concatenation of (1, 2, ..., n, n-1, ..., 1).
%H FactorDB, <a href="http://factordb.com/index.php?query=%28121*10%5E%284*n-19%29+-+1002*10%5E%284*n-28%29+-+2*10%5E%282*n-9%29+%2B+879*10%5E10+%2B+121%29%2F99%5E2&perpage=60">(121*10^(4*n-19) - 1002*10^(4*n-28) - 2*10^(2*n-9) + 879*10^10 + 121)/99^2</a>.
%F a(n) = A001222(A173426(n)).
%e a(2) = 2 since A173426(2) = 121 = 11*11 has twice the factor 11.
%e a(21) = 6 since A173426(21) = 3 * 3 * 7 * 828703 * 94364768151913037621 * 250591098443370396365457961250972909.
%o (PARI) a(n)=bigomega(A173426(n))
%Y See A260587 for the variant where only distinct prime factors are counted.
%Y See also A075023 and A075024 for the smallest and largest prime factor of the terms.
%Y Cf. A001222.
%K nonn,base,hard,more
%O 1,2
%A _M. F. Hasler_, Jul 29 2015
%E Terms beyond a(30) via factorization results by _Serge Batalov_, added by _M. F. Hasler_, Jul 30 2015
%E a(38)-a(44) added using factordb.com by _Jinyuan Wang_, Mar 05 2020
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