A179802 Digital root of A179545.

3, 9, 3, 9, 3, 9, 3, 9, 3, 3, 9, 9, 3, 9, 3, 3, 3, 9, 9, 3, 9, 9, 3, 3, 9, 3, 9, 3, 9, 3, 9, 3, 3, 9, 3, 9, 9, 9, 3, 3, 3, 9, 3, 9, 3, 9, 9, 9, 3, 9, 3, 3, 9, 3, 3, 3, 3, 9, 9, 3, 9, 3, 9, 3, 9, 3, 9, 9, 3, 9, 3, 3, 9, 9, 9, 3, 3, 9, 3, 9, 3, 9, 3, 9, 9, 3, 3

Offset: 1

Author

Odimar Fabeny, Jul 27 2010

Keywords

• easy
• nonn
• base

Comments

Because every term in A179545 is a multiple of 3, each term of this sequence is 3 or 9. - Nathaniel Johnston, May 04 2011

a(n) = 3 if and only if prime(n) == 2 (mod 3); otherwise a(n) = 9. - Charles R Greathouse IV, May 19 2011

Links

• Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A010888, A179545.

Programs

Maple

read("transforms") ; A010888 :=proc(n) local a; a := digsum(n) ; if a > 9 then return procname(a) ; else return a; end if; end proc:
A179545 := proc(n) local p; p := ithprime(n); 3*p*(p-1)/2 ; end proc:
A179802 := proc(n) A010888(A179545(n)) ; end proc:
seq(A179802(n),n=1..180) ; # R. J. Mathar, Oct 03 2010

PARI

apply(p->if(p%3==2,3,9),primes(10000)) \\ Charles R Greathouse IV, May 19 2011

Formula

a(n) = A010888(A179545(n)). - Michel Marcus, Mar 08 2022

Extensions

More terms from R. J. Mathar, Oct 03 2010