cp's OEIS Frontend

A309721 Number of right angles between the segments that are turned "on" when representing n on a 7-segment (calculator) display.

%I A309721 #14 Sep 23 2019 14:40:18
%S A309721 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 A309721 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 A309721 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 A309721 Number of right angles between the segments that are turned "on" when representing n on a 7-segment (calculator) display.
%C A309721 The display is the one described in A006942 (see also the example section below).
%F A309721 a(n) = a(floor(n/10)) + a(n mod 10), for n > 9 (a formula by _Reinhard Zumkeller_, same for A006942 and A010371).
%e A309721 To illustrate a(0),...,a(9):
%e A309721    _     _  _       _   _   _   _   _
%e A309721   | | |  _| _| |_| |_  |_    | |_| |_|
%e A309721   |_| | |_  _|   |  _| |_|   | |_|  _|
%e A309721 .
%t A309721 Evaluate[Table[a[n],{n,0,9}]]={4,0,4,4,3,4,6,1,8,6};
%t A309721 a[n_/;n>9]:=a[Floor[n/10]]+a[Mod[n,10]]; a/@Range[0,100] (* or *)
%t A309721 Table[Total[IntegerDigits[n]/.{0->4,1->0,2->4,3->4,4-> 3,5->4,7->1,9->6}],{n,0,100}]
%Y A309721 Cf. A006942, A010371, A063720, A277116.
%K A309721 nonn,base,easy
%O A309721 0,1
%A A309721 _Ivan N. Ianakiev_, Aug 14 2019