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A336121
a(1) = 0, and for n > 1, a(n) = [A122111(n) == 3 (mod 4)] + a(A253553(n)).
5
0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 1, 0, 1, 0, 2, 1, 1, 0, 1, 0, 2, 0, 3, 0, 1, 1, 1, 0, 1, 0, 2, 0, 2, 0, 1, 0, 1, 0, 3, 0, 1, 0, 1, 0, 3, 1, 2, 0, 1, 0, 1, 0, 1, 0, 3, 1, 2, 0, 1, 0, 1, 0, 2, 0, 1, 1, 1, 0, 2, 0, 3, 0, 1, 0, 1, 1, 1, 0, 2, 0, 3, 0, 1, 0, 1, 1, 3, 0, 2, 0, 2, 0, 2, 0, 2, 1
OFFSET
1,16
COMMENTS
Positions for the first occurrence of each n, for n >= 0, are: 1, 4, 16, 32, 144, 512, 2048, 6912, 20736, 62208, ...
LINKS
FORMULA
a(1) = 0, and for n > 1, a(n) = [A336124(n) == 3] + a(A253553(n)).
a(n) = A000120(A336120(n)).
a(n) = A292377(A122111(n)).
a(n) = A001222(n) - A336123(n).
PROG
(PARI)
A253553(n) = if(n<=2, 1, my(f=factor(n), k=#f~); if(f[k, 2]>1, f[k, 2]--, f[k, 1] = precprime(f[k, 1]-1)); factorback(f));
A336121(n) = if(1==n, 0, (3==A336124(n))+A336121(A253553(n)));
CROSSREFS
Cf. A336119 (positions of zeros).
Sequence in context: A263635 A373850 A358233 * A363795 A214332 A164734
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jul 17 2020
STATUS
approved