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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 (list; graph; refs; listen; history; text; internal format)
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 A109692 A039758 * 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

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Last modified December 5 02:30 EST 2022. Contains 358572 sequences. (Running on oeis4.)