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A296442 Initial digit of n-th Mersenne number. 1
3, 7, 3, 1, 2, 8, 1, 5, 8, 5, 2, 1, 2, 8, 1, 9, 5, 2, 1, 2, 9, 6, 9, 6, 1, 2, 1, 1, 6, 1, 1, 2, 1, 6, 7, 2, 1, 1, 1, 1, 7, 3, 3, 1, 2, 8, 3, 1, 2, 8, 1, 8, 3, 3, 2, 1, 9, 3, 2, 3, 1, 1, 2, 4, 1, 2, 4, 2, 2, 1, 1, 1, 3, 1, 1, 1, 1, 3, 5, 1, 1, 5, 5, 2, 1, 2, 1, 3, 5, 2, 3, 1, 3, 6, 1, 2, 1, 6, 2, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

Zhaodong Cai, Matthew Faust, A.J. Hildebrand, Junxian Li, Yuan Zhang, Leading Digits of Mersenne Numbers, arXiv:1712.04425 [math.NT], 2017.

FORMULA

a(n) = A000030(A001348(n)).

EXAMPLE

The 4th Mersenne number is 127, so a(4) = 1.

MAPLE

initialdig:= n -> floor(n/10^ilog10(n)):

seq(initialdig(2^ithprime(i)-1), i=1..100); # Robert Israel, Dec 13 2017

MATHEMATICA

Array[First@ IntegerDigits[2^Prime[#] - 1] &, 105] (* Michael De Vlieger, Dec 13 2017 *)

PROG

(PARI) a(n) = digits(2^prime(n)-1)[1];

CROSSREFS

Cf. A000030, A001348.

A135613, for Mersenne primes, is a subsequence.

Sequence in context: A153027 A161127 A256978 * A021272 A135613 A019973

Adjacent sequences:  A296439 A296440 A296441 * A296443 A296444 A296445

KEYWORD

nonn,base

AUTHOR

Michel Marcus, Dec 13 2017

STATUS

approved

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Last modified July 16 00:57 EDT 2019. Contains 325061 sequences. (Running on oeis4.)