A027386 Write digits for n, count endpoints (version 1).

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, 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, 1, 2, 2, 4, 4, 4, 4, 4, 3, 4, 2, 3, 0

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• base

Comments

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

Examples

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

Crossrefs

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

Programs

Mathematica

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 *)

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

Formula

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

Extensions

a(6) corrected and a(27)-a(80) from Andrew Howroyd, Oct 26 2017