OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
k=13 --> m=4 because binomial(13,4) = 13!/(4!*9!) = 715 --> 7+1+5 = 13.
k=75 --> m=37 because binomial(75,37) = 75!/(37!*38!)=3446310324346630677300 --> 3+4+4+6+3+1+3+2+4+3+4+6+6+3+6+7+7+3 = 75.
MAPLE
P:=proc(n) local i, j, k, w; for i from 1 by 1 to n do for j from 1 to i do w:=0; k:=binomial(i, j); while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if i=w then print(i); break; fi; od; od; end: P(200);
MATHEMATICA
sdbQ[n_]:=Module[{d=Total[IntegerDigits[#]]&/@Table[Binomial[n, m], {m, n-1}]}, MemberQ[d, n]]; Join[{1}, Select[Range[200], sdbQ]] (* Harvey P. Dale, Jan 03 2013 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, Jul 20 2007
STATUS
approved