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A255309
Number of times log_2 can be applied to n until the result is either 1 or not a power of 2. Here log_2 means the base-2 logarithm.
3
0, 0, 1, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
OFFSET
0,5
LINKS
FORMULA
a(n) = 1 + a(log_2(n)) if n is a power of 2 except 1, 0 otherwise.
PROG
(PARI) nbi(n) = {my(nb = 0); if ((ispower(n, , &m) && (m==2)) || (n==2), return(nbi(valuation(n, 2))+1); ); nb; }
a(n) = { my(nb = 0); if ((ispower(n, , &m) && (m==2)) || (n==2), return(nbi(valuation(n, 2))+1); ); nb; } \\ Michel Marcus, Mar 11 2015; corrected Jun 13 2022
(PARI) A255309(n) = { my(k=0); while((n>1)&&!bitand(n, n-1), n = valuation(n, 2); k++); (k); }; \\ Antti Karttunen, Sep 30 2018
CROSSREFS
Cf. A000079 (2^n), A007814 (2-adic valuation of n), A209229, A255308.
Sequence in context: A072325 A294929 A076948 * A335446 A376514 A335460
KEYWORD
nonn,easy
AUTHOR
Paul Boddington, Feb 20 2015
EXTENSIONS
Extended up to a(128) by Antti Karttunen, Sep 30 2018
STATUS
approved