OFFSET
1,2
COMMENTS
a(n) == 3 or 6 (mod 9) n>2.
a(n) = 3 for n in A084229.
a(n) = 6 for n = 4, 6, 8, 10, 12, 18, 20, 22, 28, 30, 32, 38, 40, 48, 86, 88, 90, 96, 98, 100, 106, 108, 116, 160, 162, 168, 170, 178, ..., 17630. - Robert G. Wilson v, Jun 27 2014
LINKS
MATHEMATICA
a[1] = 1; a[2] = 2; a[n_] := a[n] = Sum[ Total@ IntegerDigits@ a@ i, {i, n - 1}]; Array[ Total@ IntegerDigits@ a@# &, 78] (* Robert G. Wilson v, Jun 27 2014 *)
nxt[{t_, a_}]:=Module[{c=Total[IntegerDigits[t]]}, {t+c, c}]; Join[{1}, NestList[nxt, {3, 2}, 80][[;; , 2]]] (* Harvey P. Dale, Jul 13 2023 *)
PROG
(PARI) // sumdig(n)=sum(k=0, ceil(log(n)/log(10)), floor(n/10^k)%10) // an=vector(10000); a(n)=if(n<0, 0, an[n]) // an[1]=1; an[2]=2; for(n=3, 300, an[n]=sumdig(sum(k=1, n-1, a(k)))) //
(Haskell)
a084228 n = a084228_list !! (n-1)
a084228_list = 1 : 2 : f 3 where
f x = y : f (x + y) where y = a007953 x
-- Reinhard Zumkeller, Nov 13 2014
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Benoit Cloitre, Jun 21 2003
STATUS
approved