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Search: id:A065685
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| A065685 |
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Number of primes <= prime(n) which begin with a 6. |
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+0
2
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| 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
(list; graph; listen)
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OFFSET
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1,19
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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EXAMPLE
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a(17) = 0, a(18) = 1: 61 = A000040(18) is the first prime beginning with 6. a(664579) = 72257 (A000040(664579) = 9999991 is the largest prime < 10,000,000).
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PROGRAM
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(PARI) digitsIn(x)= { local(d); if (x==0, return(1)); d=1 + log(x)\log(10); if (10^d == x, d++, if (10^(d-1) > x, d--)); return(d) } MSD(x)= { return(x\10^(digitsIn(x)-1)) } { a=0; p=2; for (n=1, 1000, q=prime(n); while (p <= q, if(MSD(p) == 6, a++); p=nextprime(p+1)); write("b065685.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 26 2009]
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CROSSREFS
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A065680, A000040.
Sequence in context: A044932 A065687 A077433 this_sequence A084100 A130130 A046698
Adjacent sequences: A065682 A065683 A065684 this_sequence A065686 A065687 A065688
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KEYWORD
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base,nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 13 2001
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