A285716 a(n) = A080791(A245611(n)).

0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 2, 0, 0, 1, 1, 0, 1, 0, 0, 2, 0, 1, 1, 0, 1, 1, 0, 0, 2, 1, 0, 1, 0, 0, 2, 1, 0, 3, 0, 1, 1, 0, 1, 1, 1, 0, 2, 0, 0, 2, 0, 0, 1, 0, 1, 2, 1, 1, 1, 2, 0, 1, 0, 1, 3, 0, 0, 1, 1, 1, 2, 0, 0, 2, 1, 0, 1, 1, 0, 2, 0, 1, 2, 0, 2, 1, 0, 0, 1, 1, 1, 3, 0, 0, 2, 0, 0, 1, 1, 1, 2, 1, 0, 1, 1, 1, 1, 1, 0, 3, 0, 0, 2, 0, 1, 1, 0

Offset

1,14

Links

Antti Karttunen, Table of n, a(n) for n = 1..8192

Formula

a(1) = 0, a(2) = 1, for n > 2, a(n) = a(A285712(n)) + [n == 2 mod 3]. (Where [] is Iverson bracket, giving here 1 only if n is of the form 3k+2, and 0 otherwise.)

a(n) = A080791(A245611(n)).

For all n >= 2, a(n) = A091304(n)-1 = A000120(A244153(n))-1. - Antti Karttunen, May 31 2017

Mathematica

a[n_] := PrimeOmega[2*n - 1] - 1; a[1] = 0; Array[a, 100] (* Amiram Eldar, Jul 23 2023 *)

Prog

(Scheme)
;; First implementation uses memoization-macro definec:
(definec (A285716 n) (if (<= n 2) 0 (+ (if (= 2 (modulo n 3)) 1 0) (A285716 (A285712 n)))))
(define (A285716 n) (A080791 (A245611 n)))

Crossrefs

One less than A091304 after the initial term.

Cf. A000120, A080791, A244153, A245611, A278223, A285712, A285714, A285715.

Cf. A006254 (gives the positions of zeros after initial a(1)=0.)

Sequence in context: A260118 A128582 A213185 * A101606 A257469 A275947

Adjacent sequences: A285713 A285714 A285715 * A285717 A285718 A285719

Keyword

nonn

Author

Antti Karttunen, Apr 25 2017

Status

approved