A262520 a(n) = A262519(n) - A262518(n).

1, 1, 1, 2, 0, 1, 2, 1, 1, 3, 2, 3, 0, 3, 4, 5, 4, 5, 3, 5, 6, 7, 5, 6, 1, 6, 7, 7, 8, 8, 10, 7, 2, 10, 9, 10, 13, 9, 11, 12, 1, 1, 4, 1, 3, 3, 2, 3, 7, 2, 2, 5, 7, 4, 9, 5, 6, 5, 5, 5, 6, 5, 1, 3, 7, 2, 8, 1, 8, 3, 9, 3, 3, 2, 3, 5, 3, 4, 6, 4, 6, 7, 4, 6, 2, 6, 6, 1, 7, 7, 10, 8, 9, 8, 8, 9, 10, 8, 1, 10, 10, 10, 11, 9, 11, 12, 10, 12, 13, 12, 13, 13, -2, -1, 2, 13, 13, 14, 14, 15

Offset: 0

Author

Antti Karttunen, Oct 02 2015

Keywords

• sign

Comments

a(n) = How many steps more are needed to reach zero when starting from k = 2*n + 1 than when starting from k = 2*n and repeatedly applying the map that replaces k by k - d(k)? [Here d(k) is the number of divisors of k (A000005)]. If it takes more steps when starting from 2n than from 2n+1, then a(n) is negative.

Links

• Antti Karttunen, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000005, A049820, A155043, A262518, A262519, A262521 (positions of negative values).

Programs

Scheme

(define (A262520 n) (- (A262519 n) (A262518 n)))

Formula

a(n) = A262519(n) - A262518(n).