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A366799
Number of divisors d of n that are not of the form 4k+2, as permuted by the Doudna sequence.
2
1, 1, 2, 2, 2, 2, 3, 3, 2, 2, 4, 4, 3, 3, 4, 4, 2, 2, 4, 4, 4, 4, 6, 6, 3, 3, 6, 6, 4, 4, 5, 5, 2, 2, 4, 4, 4, 4, 6, 6, 4, 4, 8, 8, 6, 6, 8, 8, 3, 3, 6, 6, 6, 6, 9, 9, 4, 4, 8, 8, 5, 5, 6, 6, 2, 2, 4, 4, 4, 4, 6, 6, 4, 4, 8, 8, 6, 6, 8, 8, 4, 4, 8, 8, 8, 8, 12, 12, 6, 6, 12, 12, 8, 8, 10, 10, 3, 3, 6, 6, 6, 6, 9, 9
OFFSET
0,3
FORMULA
a(n) = A320111(A005940(1+n)).
PROG
(PARI)
A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); (t); };
A320111(n) = sumdiv(n, d, (2!=(d%4)));
A366799(n) = A320111(A005940(1+n));
CROSSREFS
Cf. A005940, A320111, A366800 (rgs-transform).
Cf. also A366797.
Sequence in context: A247069 A367008 A366800 * A322168 A118377 A023516
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 27 2023
STATUS
approved