

A157890


Number of primes between exponents of successive Mersenne primes.


0



0, 0, 0, 1, 0, 0, 2, 6, 5, 3, 2, 66, 12, 95, 120, 10, 115, 127, 18, 593, 29, 130, 896, 180, 155, 2032, 3759, 2104, 1841, 6960, 41452, 7555, 28715
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OFFSET

1,7


COMMENTS

a(6) = 0 since 17 is adjacent to 19 (exponent of 7th Mersenne prime); a(7) = 2 since 23 and 29 are between 19 and 31 (exponent of 8th Mersenne prime); a(8) = 6 since 37, 41, 43, 47, 53 and 59 are between 31 and 61 (exponent of 9th Mersenne prime)


LINKS

Table of n, a(n) for n=1..33.


FORMULA

a(n) = (PrimePi(A000043(n+1))PrimePi(A000043(n)))1 = (A000720(A000043(n+1))A000720(A000043(n)))1. [From Jonathan Vos Post, Mar 09 2009]


CROSSREFS

Cf. A000040, A000043, A046933
Sequence in context: A336074 A021381 A323501 * A329932 A198821 A171897
Adjacent sequences: A157887 A157888 A157889 * A157891 A157892 A157893


KEYWORD

nonn


AUTHOR

Jani Melik, Mar 08 2009, Mar 10 2009


STATUS

approved



