

A157894


Number of composite numbers between exponents of successive Mersenne primes.


0



0, 1, 1, 4, 3, 1, 9, 23, 22, 14, 17, 327, 73, 576, 803, 67, 820, 908, 151, 4672, 222, 1141, 7827, 1583, 1352, 19255, 37986, 22155, 19704, 77081, 499295, 95038, 369638, 130508, 1469735, 42125, 3694547, 6091617
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OFFSET

1,4


COMMENTS

a(1) = 0 since 2 is adjacent to 3 (exponent of 2nd Mersenne prime);
a(2) = 1 since 4 is between 3 and 5 (exponent of 3rd Mersenne prime);
a(3) = 1 since 6 is between 5 and 7 (exponent of 4th Mersenne prime);
a(4) = 4 since 8, 9, 10, and 12 are between 7 and 13 (exponent of 5th Mersenne prime).


LINKS

Table of n, a(n) for n=1..38.


MATHEMATICA

mp={ (*A000043 *) }; lst = {}; Do[ c = mp[[n + 1]]  mp[[n]]  PrimePi@ mp[[n + 1]] + PrimePi@ mp[[n]]; AppendTo[lst, c], {n, 38}]; lst (* Robert G. Wilson v, Mar 14 2009 *)


CROSSREFS

A002808, A000043, A046933
Sequence in context: A123160 A039758 A109692 * A172106 A128813 A109062
Adjacent sequences: A157891 A157892 A157893 * A157895 A157896 A157897


KEYWORD

nonn


AUTHOR

Jani Melik, Mar 08 2009, Apr 02 2009


EXTENSIONS

a(34)  a(38) from Robert G. Wilson v, Mar 14 2009


STATUS

approved



