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Write digits for n, count endpoints (version 1).
3

%I #19 Apr 28 2018 14:34:36

%S 0,2,2,2,2,2,1,2,0,1,2,4,4,4,4,4,3,4,2,3,2,4,4,4,4,4,3,4,2,3,2,4,4,4,

%T 4,4,3,4,2,3,2,4,4,4,4,4,3,4,2,3,2,4,4,4,4,4,3,4,2,3,1,3,3,3,3,3,2,3,

%U 1,2,2,4,4,4,4,4,3,4,2,3,0

%N Write digits for n, count endpoints (version 1).

%C Number of endpoints: 0,8 - zero, 6,9 - one, 1,2,3,4,5,7 - two. - _Michael B. Porter_, Oct 28 2017

%F a(10*n + d) = a(n) + e where e is the number of endpoints of single digit d. - _David A. Corneth_, Oct 28 2017

%e The digit 1 has two endpoints, and the digit 8 has no endpoints, so a(18) = 2. - _Michael B. Porter_, Oct 28 2017

%t Table[Total[IntegerDigits[n]/.{0->0,1->2,2->2,3->2,4->2,5->2,6->1,7->2,8->0,9->1}],{n,0,80}] (* _Harvey P. Dale_, Apr 28 2018 *)

%o (PARI) a(n)=vecsum(apply(d->[0, 2, 2, 2, 2, 2, 1, 2, 0, 1][d+1], digits(n))); \\ _Andrew Howroyd_, Oct 26 2017

%Y Cf. A027387, A027388, A027389, A055642, A100910, A102683, A268643.

%K nonn,base

%O 0,2

%A _N. J. A. Sloane_.

%E a(6) corrected and a(27)-a(80) from _Andrew Howroyd_, Oct 26 2017