0,3

a(0) = 0 by convention, because 0 is not present in arrays A257503 and A257505.

Antti Karttunen, Table of n, a(n) for n = 0..10080

If A257685(n) = 0, then a(n) = A257682(n), otherwise a(n) = a(A257685(n)).

(Scheme, two versions, utilizing memoizing definec-macro)

(definec (A257681 n) (if (zero? (A257685 n)) (A257682 n) (A257681 (A257685 n))))

(definec (A257681 n) (if (or (zero? n) (= 1 (A257680 n))) (A257682 n) (A257681 (A257685 n))))

Cf. A257680, A257682, A257685.

Column index of A257503, row index of A257505.

Cf. also A257679 (gives the other index).

Sequence in context: A117385 A071517 A305433 * A338240 A265755 A341130

Adjacent sequences: A257678 A257679 A257680 * A257682 A257683 A257684

nonn

Antti Karttunen, May 04 2015

approved