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

Views

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

A268415 Balanced odious numbers: numbers with an odd number of runs of 1's in their binary expansion.

Original entry on oeis.org

1, 2, 3, 4, 6, 7, 8, 12, 14, 15, 16, 21, 24, 28, 30, 31, 32, 37, 41, 42, 43, 45, 48, 53, 56, 60, 62, 63, 64, 69, 73, 74, 75, 77, 81, 82, 83, 84, 86, 87, 89, 90, 91, 93, 96, 101, 105, 106, 107, 109, 112, 117, 120, 124, 126, 127, 128, 133, 137, 138, 139, 141
Offset: 1

Views

Author

Vladimir Shevelev, Feb 04 2016

Keywords

Comments

In the balanced binary system the sequence A268411 plays the role of the Thue-Morse sequence (A010060). Therefore we call the balanced odious numbers those numbers n for which A268411(n) = 1.
Complement of A268412.

Examples

			77 is a member because its binary expansion (1001101) has 3 runs of 1's, and 3 is odd.
		

Crossrefs

Positions of odd terms in A069010.
Cf. A268412 (complement).
Cf. A268382 (the least monotonic left inverse).
Cf. A268477 (primes in this sequence).

Programs

  • Mathematica
    balancedBinary:=Join[#,{0}]-Join[{0},#]&[IntegerDigits[#,2]]&;
    Flatten[Position[Map[Mod[Count[balancedBinary[#],1],2]&,Range[0,100]],1]-1] (* Peter J. C. Moses, Feb 04 2016 *)
    Select[Range[200],OddQ[Count[Split[IntegerDigits[#,2]],?(MemberQ[ #,1]&)]]&] (* _Harvey P. Dale, Mar 31 2019 *)
  • Python
    A268415_list = [i for i in range(10**6) if len(list(filter(bool,format(i,'b').split('0')))) % 2] # Chai Wah Wu, Mar 01 2016
  • Scheme
    (define A268415 (ZERO-POS 1 1 (COMPOSE -1+ A268411))) ;; requires also my IntSeq-library. - Antti Karttunen, Feb 05 2016
    

Formula

Other identities. For all n >= 1:
A268382(a(n)) = n.

Extensions

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

A268476 Balanced evil primes: primes with an even number of runs of 1's in their binary expansion.

Original entry on oeis.org

5, 11, 13, 17, 19, 23, 29, 47, 59, 61, 67, 71, 79, 97, 103, 113, 131, 149, 173, 181, 191, 193, 199, 223, 227, 239, 241, 251, 257, 263, 271, 277, 293, 331, 337, 347, 349, 373, 383, 421, 449, 463, 479, 487, 499, 503, 509, 557, 587, 593, 599, 601, 613, 617, 619
Offset: 1

Views

Author

Vladimir Shevelev, Feb 05 2016

Keywords

Comments

Primes in A268412. Complement of A268477.

Crossrefs

Programs

  • Mathematica
    Select[Prime@ Range@ 120, EvenQ@ Length[Split@ IntegerDigits[#, 2] /. {0, _} -> Nothing] &] (* Michael De Vlieger, Feb 08 2016 *)
  • Python
    from sympy import prime
    A268476_list = [p for p in (prime(i) for i in range(1,10**6)) if not 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.