%I A072921
%S A072921 1,2,5,13,25,44,71,106,148,203,263,334,415,506,608,724,853,998,1169,
%T A072921 1357,1561,1778,2018,2269,2539,2828,3137,3460,3796,4157,4535,4930,
%U A072921 5341,5765,6212,6670,7147,7643,8159,8698,9268,9863,10484,11122
%N A072921 a(1)=1; a(n) = a(n-1) + [sum of all decimal digits present so far in 
               the sequence].
%F A072921 a(1)=1,a(2)=2; a(n+1)=2a(n)-a(n-1)+sod(a(n)) (sod = "sum of digits"). 
               - Farideh Firoozbakht (mymontain(AT)yahoo.com), Oct 01 2009
%F A072921 Asymptotically it seems a(n)~c*n^2*log(n) for c~1.99... [From Benoit 
               Cloitre (benoit7848c(AT)orange.fr), Oct 07 2009]
%p A072921 Maple program from Alois Heinz:
%p A072921 b:= proc(n) option remember; local m;
%p A072921 m:= a(n);
%p A072921 `if` (n=1, 0, b(n-1));
%p A072921 while m>0 do
%p A072921 %+ irem (m, 10, 'm')
%p A072921 od;
%p A072921 %
%p A072921 end;
%p A072921 a:= proc(n) option remember;
%p A072921 `if` (n=1, 1, a(n-1) +b(n-1))
%p A072921 end;
%p A072921 seq (a(n), n=1..50);
%t A072921 a[1]=1;a[2]=2;a[n_]:=a[n]=2*a[n-1]-a[n-2]+Apply[Plus,IntegerDigits[a[n-1]]];
               Table[a[n],{n,100}] (from Farideh Firoozbakht (mymontain(AT)yahoo.com), 
               Oct 01 2009)
%t A072921 a[1] = 1; a[n_] := a[n] = a[n - 1] + Plus @@ Flatten[ Map[ IntegerDigits, 
               Array[a, n - 1]]]; Array[a, 100] - Robert G. Wilson, v, Oct 01 2009
%Y A072921 Cf. A152231-A152234.
%Y A072921 Sequence in context: A106009 A079780 A048871 this_sequence A087250 A065301 
               A126656
%Y A072921 Adjacent sequences: A072918 A072919 A072920 this_sequence A072922 A072923 
               A072924
%K A072921 nonn,base
%O A072921 1,2
%A A072921 N. J. A. Sloane, Oct 07 2009, based on a posting to the Sequence Fans 
               Mailing List by Eric Angelini (Eric.Angelini(AT)kntv.be), Oct 01 
               2009
%E A072921 More terms from Alois Heinz, Oct 01 2009