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.

A095330 Number of A095320-primes in range ]2^n,2^(n+1)].

Original entry on oeis.org

1, 2, 2, 5, 7, 13, 23, 42, 71, 122, 241, 412, 789, 1413, 2770, 4859, 9545, 16955, 34039, 60484, 121241, 216830, 441223, 785885, 1597803, 2867949, 5874665, 10544609, 21636090, 39034399, 80414166, 145210901, 299284792
Offset: 1

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Author

Antti Karttunen, Jun 04 2004

Keywords

Comments

Ratios a(n)/A036378(n) converge as: 1, 1, 1, 1, 1, 1, 1, 0.976744, 0.946667, 0.890511, 0.945098, 0.887931, 0.904817, 0.876551, 0.914191, 0.851112, 0.88799, 0.831535, 0.881041, 0.82195, 0.863934, 0.808416, 0.858898, 0.797191, 0.84356, 0.786657, 0.835979, 0.777517, 0.825576, 0.769947, 0.819026, 0.76292, 0.81036

Crossrefs

a(n) = A036378(n)-A095331(n).

A095316 Primes in whose binary expansion the number of 1-bits is > number of 0-bits minus 2.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 263, 269, 271, 277, 281
Offset: 1

Views

Author

Antti Karttunen, Jun 04 2004

Keywords

Comments

Differs from primes (A000040) first time at n=32, where a(32)=139, while A000040(32)=131, as 131 whose binary expansion is 10000011, with 3 1-bits and 5 0-bits is the first prime excluded from this sequence.

Crossrefs

Complement of A095317 in A000040. Subset of A095320. Subset: A095074. Cf. also A095326.

Programs

  • Mathematica
    Select[Prime[Range[60]],DigitCount[#,2,1]>(DigitCount[#,2,0]-2)&] (* Harvey P. Dale, May 28 2012 *)
  • PARI
    forprime(p=2,281,v=binary(p);s=0;for(k=1,#v,s+=if(v[k]==1,+1,-1));if(s>-2,print1(p,", "))) \\ Washington Bomfim, Jan 13 2011

A095321 Primes in whose binary expansion the number of 1-bits is <= number of 0-bits minus 3.

Original entry on oeis.org

257, 521, 577, 641, 769, 1031, 1033, 1049, 1061, 1091, 1093, 1097, 1153, 1217, 1283, 1289, 1297, 1409, 1553, 1601, 2053, 2069, 2081, 2083, 2089, 2113, 2129, 2179, 2309, 2593, 2689, 3089, 3137, 3329, 4099, 4111, 4129, 4133, 4139, 4153
Offset: 1

Views

Author

Antti Karttunen, Jun 04 2004

Keywords

Crossrefs

Complement of A095320 in A000040. Subset of A095317. Cf. also A095331.

Programs

  • Maple
    filter:= proc(p) local L;
      L:= convert(p,base,2);
      2*convert(L,`+`) <= nops(L)-3
    end proc;
    select(filter, [seq(ithprime(i),i=1..1000)]); # Robert Israel, Apr 27 2025
  • Mathematica
    Select[Prime[Range[600]],DigitCount[#,2,1]<=DigitCount[#,2,0]-3&] (* Harvey P. Dale, Jul 04 2018 *)
  • PARI
    forprime(p=2, 4200, v=binary(p); s=0; for(k=1,#v, s+=if(v[k]==1,+1,-1)); if(s<=-3, print1(p,", "))) \\ Washington Bomfim, Jan 12 2011
Showing 1-3 of 3 results.