cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A268483 Primes p such that the numbers of primes not exceeding p in A268476 and A268477 are equal.

Original entry on oeis.org

13, 43, 53, 139, 151, 193, 199, 223, 229, 239, 317, 397, 4751, 4889, 4909, 4937, 4951, 4967, 5011, 5023, 5077, 5087, 5113, 5297, 5351, 5419, 6007, 6053, 6211, 6247, 6301, 6317, 6343, 6857, 9209, 9421, 9473, 9491, 10937, 11047, 11329, 11399, 11423, 11443, 11491
Offset: 1

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Author

Vladimir Shevelev, Feb 05 2016

Keywords

Comments

In contrast to the analogous sequence for odious and evil primes (A027697, A027699), which, as we conjecture, consists of only primes 3,7,29 (see also our 2007-conjecture in A027697, A027699), here we conjecture that the sequence is infinite.

Crossrefs

Programs

  • Mathematica
    lim = 1500; s = Select[Prime@ Range@ lim, EvenQ@ Length[Split@ IntegerDigits[#, 2] /. {0, _} -> Nothing] &]; t = Select[Prime@ Range@ lim, OddQ@ Length[Split@ IntegerDigits[#, 2] /. {0, _} -> Nothing] &] ; Select[Prime@ Range@ lim, Count[s, p_ /; p <= #] == Count[t, q_ /; q <= #] &] (* Michael De Vlieger, Feb 08 2016 *)

Extensions

More terms from Peter J. C. Moses, Feb 05 2016

A268412 Balanced evil numbers: numbers with an even number of runs of 1's in their binary expansion.

Original entry on oeis.org

0, 5, 9, 10, 11, 13, 17, 18, 19, 20, 22, 23, 25, 26, 27, 29, 33, 34, 35, 36, 38, 39, 40, 44, 46, 47, 49, 50, 51, 52, 54, 55, 57, 58, 59, 61, 65, 66, 67, 68, 70, 71, 72, 76, 78, 79, 80, 85, 88, 92, 94, 95, 97, 98, 99, 100, 102, 103, 104, 108, 110, 111, 113, 114
Offset: 0

Views

Author

Vladimir Shevelev, Feb 04 2016

Keywords

Comments

In balanced binary system the sequence A268411 plays role of Thue-Morse sequence (A010060). Therefore, we call the balanced evil numbers those numbers n for which A268411(n) = 0.

Examples

			In binary representation 19=10011 has an even number (two) of runs of 1's. So, 19 is a member.
		

Crossrefs

Positions of even terms in A069010.
Cf. A268415 (complement).
Cf. A268383 (the least monotonic left inverse).
Cf. A268476 (primes in this sequence).

Programs

  • Mathematica
    balancedBinary:=Join[#,{0}]-Join[{0},#]&[IntegerDigits[#,2]]&;
    Flatten[Position[Map[Mod[Count[balancedBinary[#],1],2]&,Range[0,100]],0,1]-1] (* Peter J. C. Moses, Feb 04 2016 *)
  • Python
    A268412_list = [i for i in range(10**6) if not len(list(filter(bool,format(i,'b').split('0')))) % 2] # Chai Wah Wu, Mar 01 2016

Formula

Other identities. For all n >= 0:
A268383(a(n)) = n.

Extensions

More terms from Peter J. C. Moses, Feb 04 2016

A268477 Balanced odious primes: primes with an odd number of runs of 1's in their binary expansion.

Original entry on oeis.org

2, 3, 7, 31, 37, 41, 43, 53, 73, 83, 89, 101, 107, 109, 127, 137, 139, 151, 157, 163, 167, 179, 197, 211, 229, 233, 269, 281, 283, 307, 311, 313, 317, 353, 359, 367, 379, 389, 397, 401, 409, 419, 431, 433, 439, 443, 457, 461, 467, 491, 521, 523, 541, 547, 563
Offset: 1

Views

Author

Vladimir Shevelev, Feb 05 2016

Keywords

Comments

Primes from A268415.
According to our 2007-conjecture, if pi_1(m) is the number of evil primes (A027699) not exceeding m and pi_2(m) is the number of odious primes (A027697) not exceeding m, then pi_1(m)<=pi_2(m) for all natural m except m=5 and m=6.
In the "balance" case of A268476,A268477, most likely, none of two types of primes
is in the majority beginning with any place.

Crossrefs

Programs

  • Mathematica
    Select[Prime@ Range@ 108, OddQ@ Length[Split@ IntegerDigits[#, 2] /. {0, _} -> Nothing] &] (* Michael De Vlieger, Feb 08 2016 *)
  • Python
    from sympy import prime
    A268477_list = [p for p in (prime(i) for i in range(1,10**6)) if len(list(filter(bool,format(p,'b').split('0')))) % 2] # Chai Wah Wu, Mar 01 2016

Extensions

More terms from Peter J. C. Moses, Feb 05 2016
Showing 1-3 of 3 results.