%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