A027389 Write decimal digits for n, count endpoints (version 4).

0, 2, 2, 2, 4, 2, 1, 4, 0, 1, 2, 4, 4, 4, 6, 4, 3, 6, 2, 3, 2, 4, 4, 4, 6, 4, 3, 6, 2, 3, 2, 4, 4, 4, 6, 4, 3, 6, 2, 3, 4, 6, 6, 6, 8, 6, 5, 8, 4, 5, 2, 4, 4, 4, 6, 4, 3, 6, 2, 3, 1, 3, 3, 3, 5, 3, 2, 5, 1, 2, 4, 6, 6, 6, 8, 6, 5, 8, 4, 5, 0

Offset

0,2

Comments

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

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

David A. Corneth, Image of digits with their endpoints.

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

Example

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

Mathematica

Table[Total[IntegerDigits[n]/.{1->2, 3->2, 5->2, 6->1, 7->4, 8->0, 9->1}], {n, 0, 100}] (* Harvey P. Dale, May 08 2022 *)

Prog

(PARI) a(n)=vecsum(apply(d->[0, 2, 2, 2, 4, 2, 1, 4, 0, 1][d+1], digits(n))); \\ based on program for A027386 by Andrew Howroyd, Michael B. Porter, Oct 28 2017

Crossrefs

Cf. A027386, A027387, A027388, A055642, A100910, A102683, A268643.

Sequence in context: A027387 A226534 A138260 * A337539 A374324 A111735

Adjacent sequences: A027386 A027387 A027388 * A027390 A027391 A027392

Keyword

nonn,base

Author

N. J. A. Sloane

Extensions

a(6) corrected by Michael B. Porter, Oct 28 2017 (per Andrew Howroyd)

a(27) to a(80) by Michael B. Porter, Oct 28 2017

Status

approved