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 1-6 of 6 results.

A095062 Number of fib00 primes (A095082) in range [2^n,2^(n+1)].

Original entry on oeis.org

1, 1, 2, 1, 2, 7, 12, 14, 27, 50, 91, 178, 335, 611, 1156, 2147, 4042, 7831, 14724, 28227, 53736, 102482, 196303, 376121, 723408, 1393572, 2683465, 5180304, 10009707, 19366479, 37509260, 72706948, 141074303, 273975483, 532538340
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Formula

a(n) = A095060(n) - A095067(n) = A095065(n) + A095068(n).

Extensions

a(34)-a(35) from Amiram Eldar, Jun 13 2024

A036378 Number of primes p between powers of 2, 2^n < p <= 2^(n+1).

Original entry on oeis.org

1, 1, 2, 2, 5, 7, 13, 23, 43, 75, 137, 255, 464, 872, 1612, 3030, 5709, 10749, 20390, 38635, 73586, 140336, 268216, 513708, 985818, 1894120, 3645744, 7027290, 13561907, 26207278, 50697537, 98182656, 190335585, 369323305, 717267168, 1394192236, 2712103833
Offset: 0

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Author

Keywords

Comments

Number of primes whose binary order (A029837) is n+1, i.e., those with ceiling(log_2(p)) = n+1. [corrected by Jon E. Schoenfield, May 13 2018]
First differences of A007053. This sequence illustrates how far the Bertrand postulate is oversatisfied.
Scaled for Ramanujan primes as in A190501, A190502.
This sequence appears complete such that any nonnegative number can be written as a sum of distinct terms of this sequence. The sequence has been checked for completeness up to the gap between 2^46 and 2^47. Assuming that after 2^46 the formula x/log(x) is a good approximation to primepi(x), it can be proved that 2*a(n) > a(n+1) for all n >= 46, which is a sufficient condition for completeness. [Frank M Jackson, Feb 02 2012]

Examples

			The 7 primes for which A029837(p)=6 are 37, 41, 43, 47, 53, 59, 61.
		

Crossrefs

Programs

  • Magma
    [1,1] cat [#PrimesInInterval(2^n, 2^(n+1)): n in [2..29]]; // Vincenzo Librandi, Nov 18 2014
  • Mathematica
    t = Table[PrimePi[2^n], {n, 0, 20}]; Rest@t - Most@t (* Robert G. Wilson v, Mar 20 2006 *)
  • PARI
    a(n) = primepi(1<<(n+1))-primepi(1<
    				

Formula

a(n) = primepi(2^(n+1)) - primepi(2^n).
a(n) = A095005(n)+A095006(n) = A095007(n) + A095008(n) = A095013(n) + A095014(n) = A095015(n) + A095016(n) (for n > 1) = A095021(n) + A095022(n) + A095023(n) + A095024(n) = A095019(n) + A095054(n) = A095020(n) + A095055(n) = A095060(n) + A095061(n) = A095063(n) + A095064(n) = A095094(n) + A095095(n).

Extensions

More terms from Labos Elemer, May 13 2004
Entries checked by Robert G. Wilson v, Mar 20 2006

A095061 Number of fibodd primes (A095081) in range [2^n,2^(n+1)].

Original entry on oeis.org

0, 0, 0, 2, 4, 4, 7, 18, 25, 54, 105, 178, 332, 637, 1165, 2194, 4161, 7770, 14800, 28100, 53525, 102394, 195938, 377301, 723938, 1391620, 2684760, 5178439, 10010119, 19362205, 37501838, 72702221, 141062816, 273985225, 532514962
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Formula

a(n) = A036378(n) - A095060(n) = A095066(n) + A095069(n).

Extensions

a(34)-a(35) from Amiram Eldar, Jun 13 2024

A095067 Number of fib010 primes (A095087) in range [2^n,2^(n+1)].

Original entry on oeis.org

0, 1, 0, 2, 1, 2, 4, 11, 23, 33, 59, 108, 205, 364, 709, 1368, 2546, 4789, 9111, 17259, 33075, 63340, 121467, 232396, 446774, 860552, 1659065, 3203164, 6187452, 11968853, 23171558, 44926416, 87186186, 169306460, 329138934
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Formula

a(n) = A095060(n) - A095062(n).

Extensions

a(34)-a(35) from Amiram Eldar, Jun 13 2024

A095080 Fibeven primes, i.e., primes p whose Zeckendorf-expansion A014417(p) ends with zero.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 23, 29, 31, 37, 41, 47, 71, 73, 79, 83, 89, 97, 107, 109, 113, 131, 139, 149, 151, 157, 167, 173, 181, 191, 193, 199, 223, 227, 233, 241, 251, 257, 269, 277, 283, 293, 311, 317, 337, 353, 359, 367, 379, 397, 401, 409, 419, 421
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Intersection of A000040 and A022342. Union of A095082 and A095087. Cf. A095060, A095081.

Programs

  • Maple
    F:= combinat[fibonacci]:
    b:= proc(n) option remember; local j;
          if n=0 then 0
        else for j from 2 while F(j+1)<=n do od;
             b(n-F(j))+2^(j-2)
          fi
        end:
    a:= proc(n) option remember; local p;
          p:= `if`(n=1, 1, a(n-1));
          do p:= nextprime(p);
             if b(p)::even then break fi
          od; p
        end:
    seq(a(n), n=1..100);  # Alois P. Heinz, Mar 27 2016
  • Mathematica
    F = Fibonacci;
    b[n_] := b[n] = Module[{j},
         If[n == 0, 0, For[j = 2, F[j + 1] <= n, j++];
         b[n - F[j]] + 2^(j - 2)]];
    a[n_] := a[n] = Module[{p},
         p = If[n == 1, 1, a[n - 1]]; While[True,
         p = NextPrime[p]; If[ EvenQ[b[p]], Break[]]]; p];
    Array[a, 100] (* Jean-François Alcover, Jul 01 2021, after Alois P. Heinz *)
  • 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))[-1]=="0"
    print([n for n in primerange(1, 1001) if ok(n)]) # Indranil Ghosh, Jun 07 2017

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.
Showing 1-6 of 6 results.