

A146768


Numbers k such that 2^(2k+1)  1 = A000668(n+1).


4



1, 2, 3, 6, 8, 9, 15, 30, 44, 53, 63, 260, 303, 639, 1101, 1140, 1608, 2126, 2211, 4844, 4970, 5606, 9968, 10850, 11604, 22248, 43121, 55251, 66024, 108045, 378419, 429716, 628893, 699134, 1488110, 1510688, 3486296, 6733458, 10498005, 12018291, 12982475, 15201228
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OFFSET

1,2


COMMENTS

The least common multiple of an even superperfect number greater than 2 and its arithmetic derivative divided by the number itself, i.e., lcm(A061652(i), A061652(i)')/A061652(i).  Giorgio Balzarotti, Apr 21 2011


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..46
C. K. Caldwell, Top 20 Mersenne primes
Bernhard Helmes, Prime generator f(n)=2n^21
George Woltman, Great Internet Mersenne Prime Search


FORMULA

a(n) = (A000043(n+1)  1)/2.
2^(2*a(n) + 1)  1 = A000668(n+1).  M. F. Hasler, Jan 27 2020


MATHEMATICA

(MersennePrimeExponent[Range[2, 47]]  1)/2 (* Amiram Eldar, Mar 29 2020 *)


CROSSREFS

Cf. A000043, A061652.
Sequence in context: A099381 A289943 A089437 * A211370 A122479 A334747
Adjacent sequences: A146765 A146766 A146767 * A146769 A146770 A146771


KEYWORD

nonn


AUTHOR

Artur Jasinski, Nov 02 2008


EXTENSIONS

Term for the 39th Mersenne prime added by Roderick MacPhee, Oct 05 2009
Formula and edits from Charles R Greathouse IV, Aug 14 2010
Updated to include 40th Mersenne prime by Michael B. Porter, Nov 26 2010
a(40)a(42) from Amiram Eldar, Mar 29 2020


STATUS

approved



