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 1-9 of 9 results.

A005479 Prime Lucas numbers (cf. A000032).

Original entry on oeis.org

2, 3, 7, 11, 29, 47, 199, 521, 2207, 3571, 9349, 3010349, 54018521, 370248451, 6643838879, 119218851371, 5600748293801, 688846502588399, 32361122672259149, 412670427844921037470771, 258899611203303418721656157249445530046830073044201152332257717521
Offset: 1

Views

Author

Keywords

Comments

It appears that a(n) is the intersection ( or a subset of the intersection ) of A113192[n], Primes that are the difference of two Lucas numbers and A113188[n], Primes that are the difference of two Fibonacci numbers, excluding A113192[1] = A113188[1] = 2. - Alexander Adamchuk, Aug 06 2006
For n>2 also: Primes which are the sum of four consecutive Fibonacci numbers, a(n) = A153867(n-2), cf. link to SeqFan list (Apr. 2014). - M. F. Hasler, Apr 24 2014
Conjectures: 7, 47 and 2207 are the only a(n) mod 10 = 7. They are also the only a(n) values where the Lucas index is not a prime. See A001606 for the Lucas index values of these primes. See A266587 for the divisibility of Lucas numbers by powers of primes. - Richard R. Forberg, Mar 24 2016

References

  • R. K. Guy, Unsolved Problems in Number Theory, Section A3.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Mathematica
    Select[LucasL[Range[0,250]], PrimeQ] (* Harvey P. Dale, Nov 02 2011 *)

Extensions

One further term (from the Knott web site) from Parthasarathy Nambi, Jun 27 2008

A007298 Sums of consecutive Fibonacci numbers.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 16, 18, 19, 20, 21, 26, 29, 31, 32, 33, 34, 42, 47, 50, 52, 53, 54, 55, 68, 76, 81, 84, 86, 87, 88, 89, 110, 123, 131, 136, 139, 141, 142, 143, 144, 178, 199, 212, 220, 225, 228, 230, 231, 232, 233, 288, 322
Offset: 1

Views

Author

N. J. A. Sloane, Jan 02 2000

Keywords

Comments

Also the differences between two Fibonacci numbers, because the difference F(i+2) - F(j+1) equals the sum F(j) + ... + F(i). - T. D. Noe, Oct 17 2005; corrected by Patrick Capelle, Mar 01 2008

Crossrefs

Cf. A113188 (primes that are the difference of two Fibonacci numbers).
Cf. A219114 (numbers whose squares are here).

Programs

  • Maple
    isA007298 := proc(n)
        local i,Fi,j,Fj ;
        for i from 0 do
            Fi := combinat[fibonacci](i) ;
            for j from i do
                Fj :=combinat[fibonacci](j) ;
                if Fj-Fi = n then
                    return true;
                elif Fj-Fi > n then
                    break;
                end if;
            end do:
            Fj :=combinat[fibonacci](i+1) ;
            if Fj-Fi > n then
                return false;
            end if;
        end do:
    end proc:
    for n from 0 to 100 do
        if isA007298(n) then
            printf("%d,",n) ;
        end if;
    end do: # R. J. Mathar, May 25 2016
  • Mathematica
    Union[Flatten[Table[Fibonacci[n]-Fibonacci[i], {n, 14}, {i, n}]]] (* T. D. Noe, Oct 17 2005 *)
    isA007298[n_] := Module[{i, Fi, j, Fj}, For[i = 0, True, i++, Fi = Fibonacci[i]; For[j = i, True, j++, Fj = Fibonacci[j]; Which[Fj - Fi == n, Return@True, Fj - Fi > n, Break[]]]; Fj := Fibonacci[i + 1]; If[Fj - Fi > n, Return@False]]];
    Select[Range[0, 1000], isA007298] (* Jean-François Alcover, Nov 16 2023, after R. J. Mathar *)
  • PARI
    A130233(n)=log(sqrt(5)*n+1.5)\log((1+sqrt(5))/2)
    list(lim)=my(v=List([0]),F=vector(A130233(lim),i,fibonacci(i)),s,t); for(i=1,#F, s=0; forstep(j=i,1,-1, s+=F[j]; if(s>lim, break); listput(v,s))); Set(v) \\ Charles R Greathouse IV, Oct 06 2016

Formula

log a(n) >> sqrt(n). - Charles R Greathouse IV, Oct 06 2016

A113239 Prime differences of tribonacci numbers.

Original entry on oeis.org

2, 3, 5, 11, 17, 23, 31, 37, 43, 79, 193, 491, 503, 653, 883, 1201, 10607, 19009, 19469, 19489, 34963, 35809, 46499, 223273, 223313, 391231, 409817, 410731, 532159, 634061, 754549, 1383769, 1389533, 2552621, 2555753, 3311233, 4477453, 4700621
Offset: 1

Views

Author

Jonathan Vos Post, Oct 19 2005

Keywords

Comments

A113238 is the difference set of tribonacci numbers. A113188-A113194 deal with difference sets of Fibonacci numbers and Lucas numbers and primes in those difference sets.

Examples

			a(1) = 2 because 4 - 2 = 2 where 4 and 2 are tribonacci numbers.
a(2) = 3 because 7 - 4 = 3 where 7 and 4 are tribonacci numbers.
a(3) = 5 because 7 - 2 = 5 where 7 and 2 are tribonacci numbers.
a(4) = 11 because 13 - 2 = 11 where 13 and 2 are tribonacci numbers.
a(5) = 17 because 24 - 7 = 17 where 24 and 7 are tribonacci numbers.
		

Crossrefs

Programs

  • Mathematica
    Select[Union[Flatten[Differences/@Subsets[Drop[LinearRecurrence[{1, 1, 1}, {0, 0, 1}, 29],2],{2}]]],PrimeQ] (* James C. McMahon, Jun 23 2024 *)

Formula

Intersection of primes A000040 and difference set of tribonacci numbers A113238. Positive prime values of {A000073(i) - A000073(j) such that i>j}.

A113244 Prime differences of tetranacci numbers.

Original entry on oeis.org

2, 3, 7, 11, 13, 41, 79, 107, 179, 193, 293, 397, 769, 1489, 2099, 2843, 2857, 5507, 5521, 9181, 10463, 10663, 10667, 19079, 39619, 76423, 126743, 146539, 147283, 147311, 281081, 283949, 547229, 771073, 3919171, 3919543, 3919943, 7555879, 7555927, 10644589, 14564477
Offset: 1

Views

Author

Jonathan Vos Post, Oct 19 2005; corrected Oct 20 2005

Keywords

Comments

A113188-A113194 deal with difference sets of Fibonacci numbers and Lucas numbers and primes in those difference sets. A113238-A113239 deal with the difference set of tribonacci numbers and primes in that difference set.

Examples

			a(1) = 2 because 4 - 2 = 2 where 4 and 2 are tetranacci numbers.
a(2) = 3 because 4 - 1 = 3 where 4 and 1 are tetranacci numbers.
a(3) = 7 because 8 - 1 = 7 where 8 and 1 are tetranacci numbers.
a(4) = 11 because 15 - 4 = 11 where 15 and 4 are tetranacci numbers.
a(5) = 13 because 15 - 2 = 13 where 15 and 2 are tetranacci numbers.
		

Crossrefs

Programs

  • Maple
    isA113244 := proc(n)
        isprime(n) and isA113243(n) ;
    end proc:
    for n from 1 do
        p := ithprime(n) ;
        if isA113244(p) then
            printf("%d\n",p) ;
        end if;
    end do: # R. J. Mathar, Oct 04 2014

Formula

{a(n)} = intersection of A000040 and A113243. {a(n)} = primes in the difference set of tetranacci sequence A000078, excluding prime tetranacci numbers A104535.

Extensions

281081 inserted by R. J. Mathar, Oct 04 2014

A113189 Number of times that Fibonacci(n)-Fibonacci(i) is prime for i=0..n-3.

Original entry on oeis.org

1, 2, 1, 2, 2, 1, 2, 2, 1, 2, 2, 0, 2, 1, 2, 3, 1, 1, 2, 0, 3, 3, 1, 0, 1, 1, 1, 0, 0, 2, 2, 0, 2, 5, 1, 0, 2, 0, 1, 0, 2, 0, 2, 0, 2, 2, 3, 1, 1, 2, 2, 0, 1, 1, 2, 2, 3, 7, 0, 0, 1, 0, 0, 1, 0, 1, 2, 2, 2, 1, 2, 1, 2, 1, 1, 0, 1, 0, 4, 0, 2, 6, 2, 2, 3, 0, 2, 1, 1, 0, 3, 0, 0, 6, 1, 0, 2, 5, 2, 0, 0, 1, 4, 2, 2
Offset: 3

Views

Author

T. D. Noe, Oct 17 2005

Keywords

Comments

We exclude i=n-2 and i=n-1 because they yield Fibonacci(n-2) and Fibonacci(n-1), respectively. Sequence A113190 lists the n for which a(n)=0.

Crossrefs

Cf. A113188 (primes that are the difference of two Fibonacci numbers).

Programs

  • Mathematica
    Table[cnt=0; Do[If[PrimeQ[Fibonacci[n]-Fibonacci[i]], cnt++ ], {i, 0, n-3}]; cnt, {n, 3, 150}]

A113293 First differences of Lucas 3-step numbers.

Original entry on oeis.org

0, 2, 4, 6, 8, 10, 14, 18, 20, 28, 32, 36, 38, 50, 60, 64, 68, 70, 92, 110, 120, 124, 128, 130, 170, 202, 220, 230, 234, 238, 240, 312, 372, 404, 422, 432, 436, 440, 442, 574, 684, 744, 776, 794, 804, 808, 812, 814, 1056, 1258, 1368, 1428, 1460, 1478, 1488
Offset: 1

Views

Author

Jonathan Vos Post, Oct 23 2005

Keywords

Comments

There are no primes in this sequence, except 2, as all values are odd, so all differences are even. Semiprimes include: a(3) = 4, a(4) = 6, a(6) = 10, a(7) = 14, a(13) = 38, a(26) = 202, a(35) = 422, a(44) = 794, a(54) = 1478, a(59) = 1942, a(66) = 2746, a(94) = 9326.

Examples

			a(0) = 0 because A001644(2)-A001644(0) = 3 - 3 = 0.
a(1) = 2 because A001644(2)-A001644(1) = 3 - 1 = 2.
a(2) = 4 because A001644(3)-A001644(2) = 7 - 3 = 4.
a(3) = 6 because A001644(3)-A001644(1) = 7 - 1 = 6.
a(75) = 5000 because A001644(14)-A001644(7) = 5071 - 71 = 5000.
		

Crossrefs

Formula

{a(n)} = { | A001644(i) - A001644(j) | such that i>=j}

A113190 Numbers n such that Fibonacci(n)-Fibonacci(i) is composite for all i=0..n-3.

Original entry on oeis.org

14, 22, 26, 30, 31, 34, 38, 40, 42, 44, 46, 54, 61, 62, 64, 65, 67, 78, 80, 82, 88, 92, 94, 95, 98, 102, 103, 109, 112, 113, 117, 119, 121, 122, 125, 126, 127, 134, 135, 138, 139, 142, 143, 152, 154, 155, 158, 166, 167, 170, 172, 174, 175, 176, 182, 188, 190, 193
Offset: 1

Views

Author

T. D. Noe, Oct 17 2005

Keywords

Comments

These are the n such that A113189(n)=0.

Crossrefs

Cf. A113188 (primes that are the difference of two Fibonacci numbers).

Programs

  • Mathematica
    lst={}; Do[i=0; While[iHarvey P. Dale, Nov 05 2017 *)

A113294 First differences of Lucas 4-step numbers.

Original entry on oeis.org

1, 3, 4, 8, 11, 12, 19, 22, 23, 25, 36, 44, 47, 48, 73, 84, 92, 95, 96, 140, 165, 176, 184, 187, 188, 268, 316, 341, 352, 360, 363, 364, 517, 609, 657, 682, 693, 701, 704, 705, 998, 1174, 1266, 1314, 1339, 1350, 1358, 1361, 1362, 1923, 2264, 2440, 2532, 2580
Offset: 1

Views

Author

Jonathan Vos Post, Oct 23 2005

Keywords

Comments

Lucas 4-step numbers are also known as "Tetranacci Lucas numbers" or "Tetranacci numbers with different initial conditions" in A073817. Primes in this sequence are A113295. In this sequence are: 13340261 = 11 * 19 * 29 * 31 * 71 is a product of 5 distinct 2-digit primes; 95550683 = 269 * 593 * 599 is a product of 3 distinct 3-digit primes.

Examples

			a(0) = 1 because A073817(0)-A001644(2) = 4 - 3 = 1.
a(1) = 3 because A073817(3)-A001644(0) = 7 - 4 = 3.
a(2) = 4 because A073817(3)-A001644(2) = 7 - 3 = 4.
a(3) = 8 because A073817(4)-A001644(3) = 15 - 7 = 8.
a(122) = 70000 because A073817(17)-A001644(3) = 70007 - 7 = 70000.
		

Crossrefs

Formula

{a(n)} = { | A073817(i) - A073817(j) | such that i>=j }

A113295 Prime differences of Lucas 4-step numbers.

Original entry on oeis.org

3, 11, 19, 23, 47, 73, 701, 1361, 4363, 9067, 9749, 17477, 18743, 18839, 36293, 70003, 116101, 134917, 366437, 465061, 498749, 501013, 1844033, 3590099, 13305307, 13341259, 13341619, 36229121, 49069367, 49570721, 95550661, 351427309
Offset: 1

Views

Author

Jonathan Vos Post, Oct 23 2005

Keywords

Comments

These are primes from the sequence A113294, which is differences of Lucas 4-step numbers, also known as "Tetranacci Lucas numbers" or "Tetranacci numbers with different initial conditions" in A073817. Also in the difference set sequence are: 13340261 = 11 * 19 * 29 * 31 * 71 is a product of 5 distinct 2-digit primes; 95550683 = 269 * 593 * 599 is a product of 3 distinct 3-digit primes.

Examples

			a(1) = 3 because A073817(0)-A001644(1) = 4 - 1 = 3, a prime.
a(2) = 11 because A073817(4)-A001644(0) = 15 - 4 = 11, a prime.
a(3) = 19 because A073817(5)-A001644(3) = 26 - 7 = 19, a prime.
a(4) = 23 because A073817(5)-A001644(2) = 26 - 3 = 23, a prime.
a(16) = 70003 because A073817(17)-A001644(0) = 70007 - 4 = 70003, a prime.
		

Crossrefs

Formula

{a(n)} = Intersection of { | A073817(i) - A073817(j) | such that i>=j} and A000040. {a(n)} = Prime elements of { | A073817(i) - A073817(j) | such that i>=j}. {a(n)} = Prime elements of A113294.
Showing 1-9 of 9 results.