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 A245770 Prime sieve of Pi. 8
 1, 9, 6, 5, 93, 84626, 3, 2, 502884, 69399, 5105820, 4944, 2, 816406286, 986, 4825342, 70, 9, 480865, 2, 66, 93, 55058, 25, 4081284, 174, 270, 85, 555964462, 4895, 9644288, 7566, 344, 28475648, 8, 65, 201, 45648, 23, 4543, 393, 2602, 412, 724, 660, 55, 74881, 20962, 25, 1715364, 892, 600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Robert G. Wilson v, Table of n, a(n) for n = 1..1029 (first 422 terms from Manfred Scheucher) Manfred Scheucher, Sage Script (Note: should also run in pure python with a few modifications) EXAMPLE Find the first occurrence of prime 2 in the digits of Pi (only 25 digits in this illustration): 3141592653589793238462643..., and replace it with a space: 314159 653589793238462643...  Repeat the process with 3: 14159 653589793238462643...  Then 5: 141 9 653589793238462643...  Then 7: 141 9 653589 93238462643...  Then 11, 13, 17, etc., until the first occurrence of every prime is eliminated from the digits of Pi. 1   9 6  5   93  84626  ...  Then consolidate gaps between the remaining digits into a single comma: 1,9,6,5,93,84626,...         to produce the first terms in the prime sieve of Pi. PROG (Python) def arccot(x, unity): ....sum = xpower = unity // x ....n = 3 ....sign = -1 ....while 1: ........xpower = xpower // (x*x) ........term = xpower // n ........if not term: ............break ........sum += sign * term ........sign = -sign ........n += 2 ....return sum def pi(digits): ....unity = 10**(digits + 10) ....pi = 4 * (4*arccot(5, unity) - arccot(239, unity)) ....return pi // 10**10 def primes(n): ....""" Returns  a list of primes < n """ ....sieve = [True] * n ....for i in xrange(3, int(n**0.5)+1, 2): ........if sieve[i]: ............sieve[i*i::2*i]=[False]*((n-i*i-1)/(2*i)+1) ....return [2] + [i for i in xrange(3, n, 2) if sieve[i]] a = pi(370) b = primes(100000000) y = str(a) for x in b: ....if str(x) in y: ........y = y.replace(str(x), " ", 1)#replace first occurrence only ........ while "  " in y: ....y = y.replace("  ", " ")#replace long chains of spaces with a single space z = y.split(" ")#split terms into a list z = filter(None, z)#remove null terms f = map(int, z)#convert to integers print(f[0:-1]) # David Consiglio, Jr., Jan 03 2015 CROSSREFS Cf. A000796, A246022, A248804 (Prime sieve of e), A248831 (Prime sieve of sqrt(2)). Sequence in context: A144665 A019884 A103814 * A117020 A011459 A100044 Adjacent sequences:  A245767 A245768 A245769 * A245771 A245772 A245773 KEYWORD nonn,base AUTHOR Gil Broussard, Aug 01 2014 EXTENSIONS a(14) corrected by Manfred Scheucher, May 25 2015 STATUS approved

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Last modified August 24 02:32 EDT 2019. Contains 326260 sequences. (Running on oeis4.)