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A285716
a(n) = A080791(A245611(n)).
6
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
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. A006254 (gives the positions of zeros after initial a(1)=0.)
Sequence in context: A260118 A128582 A213185 * A101606 A257469 A275947
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 25 2017
STATUS
approved