1,2

Ray Chandler, Table of n, a(n) for n = 1..322 (first 280 terms from Max Alekseyev)

a(n) = A001221(A002283(n)) = A001221(10^n - 1).

a(n) = A001221(R_n) + (n^2 mod 3) = A095370(n) + (n^2 mod 3), where R_n = (10^n-1)/9 = A002275(n). That is, a(n) = A095370(n) for n=3k; otherwise a(n) = A095370(n) + 1. - Lekraj Beedassy, Jun 09 2006

A102347 := proc(n)

10^n-1 ;

A001221(%) ;

end proc: # R. J. Mathar, Dec 02 2016

Table[PrimeNu[10^n-1], {n, 100}] (* The program will take a long time to execute *) (* Harvey P. Dale, Jan 18 2015 *)

(PARI) a(n) = omega(10^n-1); \\ Michel Marcus, Apr 22 2017

Cf. A001221, A002283, A070528.

Sequence in context: A079375 A069933 A204987 * A230846 A204908 A263027

Adjacent sequences: A102344 A102345 A102346 * A102348 A102349 A102350

nonn

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Feb 20 2005

approved