|
|
A065687
|
|
Number of primes <= prime(n) which begin with an 8.
|
|
2
|
|
|
0, 0, 0, 0, 0, 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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,24
|
|
LINKS
|
|
|
EXAMPLE
|
83 = A000040(23) is the first prime beginning with an 8, so a(23) = 1 and a(i) = 0 for i < 23. a(664579) = 71038 (A000040(664579) = 9999991 is the largest prime < 10,000,000).
|
|
MATHEMATICA
|
Accumulate[If[First[IntegerDigits[#]] == 8, 1, 0]&/@Prime[Range[100]]] (* Vincenzo Librandi, Nov 28 2016 *)
|
|
PROG
|
(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) == 8, a++); p=nextprime(p+1)); write("b065687.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 26 2009
|
|
CROSSREFS
|
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|