A309721 - OEIS

%I #14 Sep 23 2019 14:40:18

%S 4,0,4,4,3,4,6,1,8,6,4,0,4,4,3,4,6,1,8,6,8,4,8,8,7,8,10,5,12,10,8,4,8,

%T 8,7,8,10,5,12,10,7,3,7,7,6,7,9,4,11,9,8,4,8,8,7,8,10,5,12,10,10,6,10,

%U 10,9,10,12,7,14,12,5,1,5,5,4,5,7,2,9,7,12,8,12,12,11,12,14,9,16,14,10,6,10,10,9,10,12,7

%N Number of right angles between the segments that are turned "on" when representing n on a 7-segment (calculator) display.

%C The display is the one described in A006942 (see also the example section below).

%F a(n) = a(floor(n/10)) + a(n mod 10), for n > 9 (a formula by _Reinhard Zumkeller_, same for A006942 and A010371).

%e To illustrate a(0),...,a(9):

%e    _     _  _       _   _   _   _   _

%e   | | |  _| _| |_| |_  |_    | |_| |_|

%e   |_| | |_  _|   |  _| |_|   | |_|  _|

%e .

%t Evaluate[Table[a[n],{n,0,9}]]={4,0,4,4,3,4,6,1,8,6};

%t a[n_/;n>9]:=a[Floor[n/10]]+a[Mod[n,10]]; a/@Range[0,100] (* or *)

%t Table[Total[IntegerDigits[n]/.{0->4,1->0,2->4,3->4,4-> 3,5->4,7->1,9->6}],{n,0,100}]

%Y Cf. A006942, A010371, A063720, A277116.

%K nonn,base,easy

%O 0,1

%A _Ivan N. Ianakiev_, Aug 14 2019