2,2

a(n) is the least k larger than n for which the number of divisors of A048675(k) is equal to the number of divisors of A048675(n) (counted with multiplicity), and 0 if no such number exists (which happens only for n=2).

Antti Karttunen, Table of n, a(n) for n = 2..102 (computed from the b-file provided by Hans Havermann for A277892)

For n >= 3, A277894(a(n)) = n.

(Scheme) (define (A277893 n) (cond ((= 2 n) 0) (else (let ((v (A277892 n))) (let loop ((k (+ 1 n))) (if (= (A277892 k) v) k (loop (+ 1 k))))))))

Cf. A048675, A277892, A277894, A277898.

Sequence in context: A218036 A236536 A084335 * A197575 A201660 A341577

Adjacent sequences: A277890 A277891 A277892 * A277894 A277895 A277896

nonn

Antti Karttunen, Nov 08 2016

approved