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 A209385 Values of the first prefixing digits for Mersenne primes. 1
 1, 1, 1, 4, 1, 10, 1, 36, 15, 58, 57, 55, 310, 177, 51, 2389, 973, 532, 1750, 63, 1032, 1240, 3757, 9994, 5854, 12870, 46147, 11923, 17113, 10296, 5977 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS Henri Lifchitz and Renaud Lifchitz, PRP Top Records EXAMPLE For Mersenne 5, i.e., 8191, the first computed prefix is equal to 1 and gives 18191 which is also a prime, so a(5) = 1. MATHEMATICA pfx[n_] := Module[{w = 10^(1+Floor[Log10[n]])}, k=n+w ; While[!PrimeQ[k], k+=w]; Floor[k/w]]; s={}; Do[m = 2^MersennePrimeExponent[n]-1; AppendTo[s, pfx[m]], {n, 1, 12}]; s (* Amiram Eldar, Nov 22 2018 based on Andrew Howroyd's pari code *) PROG (PARI) pfx(n)={my(w=10^(1+logint(n, 10)), k=n+w); while(!ispseudoprime(k), k+=w); k\w} { for(n=1, 500, my(p=1<

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Last modified May 23 13:24 EDT 2022. Contains 353975 sequences. (Running on oeis4.)