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.

Previous Showing 91-100 of 143 results. Next

A095079 Primes with two 0-bits in their binary expansion.

Original entry on oeis.org

19, 43, 53, 79, 103, 107, 109, 367, 379, 431, 439, 443, 463, 487, 491, 499, 751, 863, 887, 983, 1013, 1279, 1471, 1531, 1663, 1759, 1783, 1787, 1789, 1951, 1979, 1999, 2011, 2027, 2029, 3067, 3581, 3823, 4027, 5119, 6079, 6911, 7039, 7103
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Cf. A095059.

Programs

  • Mathematica
    Select[Prime[Range[1000]], DigitCount[#, 2, 0] == 2 &]
  • PARI
    { forprime(p=2,8000,
      v=binary(p); s=0;
      for(k=1,#v, s+=if(v[k]==0,+1,0));
      if(s==2,print1(p,", "))
    ) }
    
  • Python
    from sympy import isprime
    from itertools import combinations, count, islice
    def agen(): # generator of terms
        for d in count(2):
            b = (1<<(d+2))-1
            for i, j in combinations(range(d), 2):
                if isprime(t:=b-(1<<(d-i))-(1<<(d-j))):
                    yield t
    print(list(islice(agen(), 43))) # Michael S. Branicky, Dec 27 2023

A095085 Fib000 primes, i.e., primes p whose Zeckendorf-expansion A014417(p) ends with three zeros.

Original entry on oeis.org

5, 13, 29, 47, 73, 89, 97, 107, 131, 149, 157, 173, 191, 199, 233, 241, 251, 293, 317, 419, 461, 479, 487, 521, 547, 563, 631, 673, 683, 691, 733, 751, 809, 827, 877, 911, 919, 937, 953, 971, 1013, 1021, 1039, 1063, 1097, 1123, 1249, 1259
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Intersection of A000040 and A101345.

Programs

  • Python
    from sympy import fibonacci, primerange
    def a(n):
        k=0
        x=0
        while n>0:
            k=0
            while fibonacci(k)<=n: k+=1
            x+=10**(k - 3)
            n-=fibonacci(k - 1)
        return x
    def ok(n): return str(a(n))[-3:]=="000"
    print([n for n in primerange(1, 1261) if ok(n)]) # Indranil Ghosh, Jun 08 2017

A095086 Fib001 primes, i.e., primes p whose Zeckendorf-expansion A014417(p) ends with two zeros and final 1.

Original entry on oeis.org

19, 43, 53, 61, 103, 137, 163, 179, 197, 229, 239, 263, 281, 307, 331, 349, 383, 433, 467, 509, 569, 577, 619, 653, 739, 773, 797, 823, 839, 857, 883, 907, 941, 967, 1009, 1051, 1061, 1069, 1103, 1129, 1153, 1171, 1187, 1213, 1229, 1289
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Intersection of A000040 and A095098. Cf. A014417, A095066.

Programs

  • Python
    from sympy import fibonacci, primerange
    def a(n):
        k=0
        x=0
        while n>0:
            k=0
            while fibonacci(k)<=n: k+=1
            x+=10**(k - 3)
            n-=fibonacci(k - 1)
        return x
    def ok(n): return str(a(n))[-3:]=="001"
    print([n for n in primerange(1, 1301) if ok(n)]) # Indranil Ghosh, Jun 08 2017

A095089 Fib101 primes, i.e., primes p whose Zeckendorf-expansion A014417(p) ends as one, zero, one.

Original entry on oeis.org

17, 59, 67, 101, 127, 211, 271, 313, 347, 373, 389, 449, 457, 491, 499, 593, 601, 643, 661, 677, 787, 821, 881, 983, 991, 1033, 1093, 1109, 1237, 1279, 1321, 1381, 1423, 1499, 1559, 1567, 1601, 1609, 1669, 1753, 1787, 1847, 1889, 1931, 1999
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Intersection of A000040 and A134860. Cf. A014417, A095069.

Programs

  • Python
    from sympy import fibonacci, primerange
    def a(n):
        k=0
        x=0
        while n>0:
            k=0
            while fibonacci(k)<=n: k+=1
            x+=10**(k - 3)
            n-=fibonacci(k - 1)
        return x
    def ok(n): return str(a(n))[-3:]=="101"
    print([n for n in primerange(1, 2001) if ok(n)]) # Indranil Ghosh, Jun 08 2017

A095090 Number of 4k+3 integers in range ]2^n,2^(n+1)] whose Jacobi-vector is a Motzkin-path (A095100).

Original entry on oeis.org

1, 1, 2, 3, 6, 9, 17, 33, 60, 108, 202, 360, 703, 1328, 2519, 4779, 9103, 17501, 33473, 64761
Offset: 1

Views

Author

Antti Karttunen and Jun 01 2004

Keywords

Crossrefs

Programs

  • PARI
    is(m) = {my(s=0); for(i=1, m-1, if((s+=kronecker(i, m))<0, return(0))); 1; }
    a(n) = {my(c=0); forstep(m=2^n+3-(n==1), 2^(n+1), 4, c+=is(m)); c; } \\ Jinyuan Wang, Jul 20 2020

Formula

a(n) = 2^(n-2) - A095091(n) for n > 1.

A095108 Diving index of the n-th diving 4k+3 prime (A095103(n)).

Original entry on oeis.org

3, 3, 3, 7, 7, 3, 3, 11, 3, 13, 61, 3, 3, 3, 7, 45, 3, 7, 7, 35, 7, 35, 3, 3, 3, 3, 15, 3, 15, 3, 7, 3, 45, 3, 3, 3, 7, 7, 3, 3, 3, 7, 7, 67, 3, 7, 3, 7, 3, 7, 57, 7, 3, 7, 15, 7, 45, 7, 23, 3, 3, 11, 7, 3, 89, 13, 55, 3, 45, 35, 3, 7, 7, 3, 3, 3, 13, 7, 15, 3, 19, 3, 7, 3, 7, 3, 99
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Nonzero terms of A095104. Cf. A095271.

A095281 Upper Wythoff primes, i.e., primes in A001950.

Original entry on oeis.org

2, 5, 7, 13, 23, 31, 41, 47, 73, 83, 89, 107, 109, 149, 151, 157, 167, 191, 193, 227, 233, 251, 269, 277, 293, 311, 337, 353, 379, 397, 421, 431, 439, 463, 479, 523, 541, 547, 557, 599, 607, 617, 641, 659, 683, 691, 701, 709, 719, 727, 733, 743
Offset: 1

Views

Author

Antti Karttunen, Jun 04 2004

Keywords

Comments

Contains all primes p whose Zeckendorf-expansion A014417(p) ends with an odd number of 0's.

Crossrefs

Intersection of A000040 & A001950. Complement of A095280 in A000040. Cf. A095081, A095083, A095084, A095290.

Programs

  • Python
    from math import isqrt
    from itertools import count, islice
    from sympy import isprime
    def A095281_gen(): # generator of terms
        return filter(isprime,((n+isqrt(5*n**2)>>1)+n for n in count(1)))
    A095281_list = list(islice(A095281_gen(),30)) # Chai Wah Wu, Aug 16 2022

A095290 Number of lower Wythoff primes (A095280) in range ]2^n,2^(n+1)].

Original entry on oeis.org

1, 0, 1, 3, 5, 8, 14, 30, 40, 86, 162, 289, 541, 1017, 1881, 3527, 6652, 12641, 23855, 45455, 86753, 165844, 317363, 609942, 1171377, 2253588, 4343268, 8381084, 16198859, 31329311, 60683252, 117637523, 228259189
Offset: 1

Views

Author

Antti Karttunen, Jun 04 2004

Keywords

Crossrefs

a(n) = A036378(n)-A095291(n). Cf. A095060, A095291.

A095296 Number of A095286-primes in range ]2^n,2^(n+1)].

Original entry on oeis.org

1, 1, 2, 3, 5, 5, 16, 21, 48, 69, 175, 229, 529, 768, 1850, 2860, 6276, 10252, 23248, 36563, 81622, 133739, 300311, 491193, 1091809, 1816561, 4062176, 6772098, 15021634, 25284670, 56134342, 94895078, 209889612
Offset: 1

Views

Author

Antti Karttunen, Jun 04 2004

Keywords

Comments

Ratios a(n)/A036378(n) converge as: 1, 0.5, 1, 0.6, 0.714286, 0.384615, 0.695652, 0.488372, 0.64, 0.50365, 0.686275, 0.493534, 0.606651, 0.476427, 0.610561, 0.500963, 0.583868, 0.502795, 0.601734, 0.496874, 0.581618, 0.498624, 0.584595, 0.498259, 0.57642, 0.498269, 0.578057, 0.499347, 0.573186, 0.498736, 0.571734, 0.498567, 0.568309
Ratios a(n)/A095335(n) converge as: 1, 1, 1, 1.5, 1.25, 0.625, 0.842105, 0.954545, 1.116279, 1.014706, 1.100629, 0.974468, 0.985102, 0.909953, 0.966562, 1.003861, 0.984008, 1.011245, 1.00445, 0.987575, 0.991822, 0.994512, 0.988408, 0.993061, 0.99389, 0.9931, 0.99673, 0.997392, 0.997286, 0.994955, 0.995265, 0.994285, 0.996248

Crossrefs

a(n) = A036378(n)-A095297(n). Cf. A095298.

A095320 Primes in whose binary expansion the number of 1-bits is > number of 0-bits minus 3.

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, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 263, 269
Offset: 1

Views

Author

Antti Karttunen, Jun 04 2004

Keywords

Comments

Differs from primes (A000040) first time at n=55, where a(55)=263, while A000040(55)=257, as 257 whose binary expansion is 100000001, with 2 1-bits and 7 0-bits is the first prime excluded from this sequence. Note that 129 (10000001 in binary, 2 1-bits and 6 0-bits) is not prime.

Crossrefs

Complement of A095321 in A000040. Subset: A095316.
Cf. A095330.

Programs

  • Mathematica
    Select[Prime[Range[60]],DigitCount[#,2,1]>DigitCount[#,2,0]-3&] (* Harvey P. Dale, Jul 24 2013 *)
  • PARI
    forprime(p=2,269,v=binary(p);s=0;for(k=1,#v,    s+=if(v[k]==1,+1,-1));if(s>-3,print1(p,", "))) \\ Washington Bomfim, Jan 13 2011
Previous Showing 91-100 of 143 results. Next