A326821 a(n) is the number of positive numbers k < n such that n+k and n-k have no digit in common.

0, 1, 2, 3, 4, 4, 4, 5, 6, 7, 6, 7, 6, 6, 7, 8, 9, 11, 12, 13, 14, 13, 13, 13, 13, 14, 16, 17, 19, 20, 19, 20, 20, 19, 20, 22, 22, 24, 25, 26, 26, 27, 26, 27, 26, 28, 29, 31, 32, 32, 32, 31, 32, 32, 35, 33, 33, 32, 32, 32, 31, 30, 30, 30, 31, 36, 34, 35, 36

Offset

1,3

Links

Michel Marcus, Table of n, a(n) for n = 1..10000

Example

For n = 7, the pairs (sum, difference) for k = 1..6 are (8, 6), (9, 5), (10, 4), (11, 3), (12, 2), (13, 1). The last two pairs are not allowed so a(7) = 4.

Prog

(PARI) ok(a, b)=length(setintersect(Set(digits(a+b)), Set(digits(a-b))))==0;
count(n)={c=0; for(k=1, n-1, if(ok(n, k), c++)); c};
a(limit)=vector(limit, n, count(n));

Crossrefs

Cf. A328021, A328289.

Sequence in context: A006158 A340203 A135414 * A356992 A099479 A120508

Adjacent sequences: A326818 A326819 A326820 * A326822 A326823 A326824

Keyword

nonn,base

Author

Lars Blomberg, Oct 20 2019

Status

approved