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A268353
a(n) is the exponent of 2 corresponding to the n-th Proth prime.
1
1, 2, 2, 4, 3, 5, 4, 6, 4, 8, 5, 6, 6, 7, 5, 8, 5, 7, 6, 7, 6, 6, 7, 6, 6, 8, 7, 7, 7, 7, 7, 9, 8, 8, 7, 7, 7, 9, 7, 9, 7, 12, 10, 7, 7, 8, 8, 7, 10, 7, 9, 11, 10, 8, 9, 8, 10, 9, 8, 8, 8, 9, 8, 9, 8, 10, 10, 8, 13, 8, 8, 9, 8, 8, 8, 10, 9, 8, 8, 10, 11
OFFSET
1,2
COMMENTS
a(n) = m where A080076(n) = k*2^m + 1, k odd.
LINKS
FORMULA
a(n) = A007814(A080076(n)-1).
EXAMPLE
The first Proth prime A080076(1) = 3 = 1*2^1 + 1, so a(1) = 1.
The second Proth prime A080076(2) = 5 = 1*2^2 + 1, so a(2) = 2.
MAPLE
N:= 10^6: # for all Proth primes <= N
Proth:= sort(convert(select(isprime, {seq(seq(k*2^m+1, k = 1 .. min(2^m, (N-1)/2^m), 2), m=1..ilog2(N-1))}), list)):
map(t -> padic:-ordp(t-1, 2), Proth);
CROSSREFS
Sequence in context: A329439 A132802 A341947 * A204900 A070803 A071693
KEYWORD
nonn
AUTHOR
Robert Israel, Feb 02 2016
STATUS
approved