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 A263856 Let S_n be the list of the first n primes written in binary, with least significant bits on the left, and sorted into lexicographic order; a(n) = position of n-th prime in S_n. 4
 1, 2, 2, 4, 4, 3, 2, 6, 9, 5, 11, 4, 3, 11, 14, 6, 13, 9, 11, 17, 3, 20, 14, 5, 2, 9, 23, 20, 12, 4, 31, 17, 5, 23, 12, 32, 17, 22, 32, 15, 26, 14, 42, 2, 11, 37, 29, 46, 27, 14, 9, 48, 6, 40, 2, 43, 22, 51, 18, 12, 43, 17, 39, 56, 14, 32, 45, 6, 50 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(A264647(n)) = n and a(m) != n for m < A264647(n). - Reinhard Zumkeller, Nov 19 2015 A264662(n,a(n)) = A000040(n): a(n) = index of prime(n) in n-th row of triangle A264662. - Reinhard Zumkeller, Nov 20 2015 LINKS John Bodeen, Table of n, a(n) for n = 1..24771 EXAMPLE S_1 = [01], a(1) = 1; S_2 = [01, 11], a(2) = 2; S_3 = [01, 101, 11], a(3) = 2; S_4 = [01, 101, 11, 111], a(4) = 4; S_5 = [01, 101, 11, 1101, 111], a(5) = 4; S_5 = [01, 101, 1011, 11, 1101, 111], a(6) = 3; ... MAPLE s:= proc(n) s(n):= cat("", convert(ithprime(n), base, 2)[]) end: a:= n-> ListTools[BinarySearch](sort([seq(s(i), i=1..n)]), s(n)): seq(a(n), n=1..100);  # Alois P. Heinz, Nov 19 2015 PROG (Haskell) import Data.List (insertBy); import Data.Function (on) import Data.List (elemIndex); import Data.Maybe (fromJust) a263856 n = a263856_list !! (n-1) a263856_list = f [] a004676_list where    f bps (x:xs) = y : f bps' xs where      y = fromJust (elemIndex x bps') + 1      bps' = insertBy (compare `on` (reverse . show)) x bps -- Reinhard Zumkeller, Nov 19 2015 (Python) from sympy import prime def A263856(n):     return 1+sorted(format(prime(i), 'b')[::-1] for i in range(1, n+1)).index(format(prime(n), 'b')[::-1]) # Chai Wah Wu, Nov 22 2015 CROSSREFS A004676 is the sequence upon which the lexicographic ordering is based. Cf. A264596. Cf. A264647, A264662. Sequence in context: A290633 A038674 A182923 * A090277 A024222 A196063 Adjacent sequences:  A263853 A263854 A263855 * A263857 A263858 A263859 KEYWORD nonn,base AUTHOR John Bodeen, Oct 28 2015 STATUS approved

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Last modified October 22 18:38 EDT 2018. Contains 316500 sequences. (Running on oeis4.)