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 1-10 of 12 results. Next

A048553 a(n+1) is next smallest prime beginning with a(n), initial prime is 11.

Original entry on oeis.org

11, 113, 11311, 113111, 1131113, 11311133, 1131113353, 113111335313, 11311133531339, 113111335313399, 1131113353133993, 113111335313399321, 11311133531339932153, 1131113353133993215379, 113111335313399321537911
Offset: 0

Views

Author

Patrick De Geest, May 15 1999

Keywords

Crossrefs

Programs

  • Maple
    f:= proc(n)
      local p, d;
      for d from 1 do
        p:= nextprime(n*10^d);
        if p < (n+1)*10^d then return p fi
      od
    end proc:
    A[1]:= 11:
    for n from 2 to 20 do A[n]:= f(A[n-1]) od:
    seq(A[n], n=1..20); # Robert Israel, Aug 16 2015
  • Mathematica
    a = {11}; Do[k = 1; w = IntegerDigits[a[[n - 1]]];
    While[CompositeQ@ FromDigits[Join[w, IntegerDigits@ k]], k += 2];
    AppendTo[a, FromDigits[Join[w, IntegerDigits@ k]]], {n, 2, 15}]; a (* Michael De Vlieger, Sep 21 2015 *)

A048556 p(n+1) is next smallest prime beginning with p(n), initial prime is 19.

Original entry on oeis.org

19, 191, 1913, 19139, 1913903, 19139039, 191390393, 19139039303, 1913903930321, 191390393032123, 1913903930321233, 191390393032123361, 19139039303212336171, 1913903930321233617139, 191390393032123361713943
Offset: 0

Views

Author

Patrick De Geest, May 15 1999

Keywords

Crossrefs

A048552 a(n+1) is next smallest prime beginning with a(n), initial prime is a(0) = 7.

Original entry on oeis.org

7, 71, 719, 7193, 71933, 719333, 71933317, 719333177, 71933317711, 7193331771103, 71933317711039, 7193331771103939, 719333177110393913, 7193331771103939133, 719333177110393913323, 71933317711039391332309, 719333177110393913323097, 719333177110393913323097047
Offset: 0

Views

Author

Patrick De Geest, May 15 1999

Keywords

Crossrefs

Programs

  • Maple
    f:= proc(n) option remember; local q,d,v;
        q:=procname(n-1);
        for d from 1 do
          v:= nextprime(q*10^d);
          if v < (q+1)*10^d then return v fi
        od
    end proc:
    f(0):= 7:
    map(f, [$0..20]); # Robert Israel, Jan 26 2020
  • Mathematica
    Nest[Function[{a, n}, Append[#, Catch@ Do[Do[If[PrimeQ@ #, Throw@ #; Break[], #] &@ FromDigits[n~Join~PadLeft[IntegerDigits[(5 j - 4 + Mod[3 j + 2, 4])/2], i]], {j, 4*10^(i - 1)}], {i, Infinity}]]] @@ {#, IntegerDigits[#[[-1]] ]} &, {7}, 17] (* Michael De Vlieger, Jan 26 2020 *)
  • PARI
    next_A048552(p)=for(i=1,oo,my(q=nextprime(p*=10));q-p>10^i||return(q))
    A048552(n,p=7)=vector(n,i,i>1&&p=next_A048552(p);p) \\ M. F. Hasler, Jan 26 2020

A048550 a(n+1) is the next smallest prime beginning with a(n), initial prime is 3.

Original entry on oeis.org

3, 31, 311, 3119, 31193, 3119309, 31193093, 311930933, 31193093317, 311930933179, 3119309331797, 311930933179703, 31193093317970371, 3119309331797037107, 311930933179703710759, 31193093317970371075907
Offset: 0

Views

Author

Patrick De Geest, May 15 1999

Keywords

Crossrefs

Programs

  • Maple
    f:= proc(n) local d,a;
      for d from 1 do
        for a from 10^d*n+1 by 2 to 10^d*(n+1) do
          if isprime(a) then return a fi
      od od
    end proc:
    R:= 3: x:= 3:
    for i from 2 to 30 do
      x:= f(x);
      R:= R, x;
    od:
    R; # Robert Israel, Dec 13 2023

A048555 p(n+1) is next smallest prime beginning with p(n), initial prime is 17.

Original entry on oeis.org

17, 173, 1733, 17333, 1733309, 173330917, 1733309173, 17333091733, 1733309173319, 173330917331917, 17333091733191701, 1733309173319170103, 173330917331917010357, 17333091733191701035703
Offset: 0

Views

Author

Patrick De Geest, May 15 1999

Keywords

Crossrefs

A055011 a(n+1) = next smallest prime beginning with a(n) when written in binary, starting with 2.

Original entry on oeis.org

2, 5, 11, 23, 47, 191, 383, 3067, 12269, 196307, 6281839, 50254717, 201018869, 804075479, 1608150959, 102921661397, 1646746582367, 13173972658937, 105391781271503, 210783562543007, 3372537000688127, 26980296005505019, 863369472176160611, 6906955777409284889
Offset: 0

Views

Author

Henry Bottomley, May 31 2000

Keywords

Comments

a(5)=191 because a(4)=47 which in binary is 101111, none of 1011110(94) 1011111(95) 10111100(188) 10111101(189) 10111110 (190) are prime, but 10111111(191) is.

Crossrefs

Cf. A048549 for base 10 analog.
A055011, A261200 and A261201 are all essentially the same sequence.

Programs

  • Haskell
    a055011 n = a055011_list !! n
    a055011_list = iterate a208241 2  -- Reinhard Zumkeller, Feb 14 2013
  • Maple
    A055011 := proc(n)
        option remember;
        if n = 0 then
            2 ;
        else
            A208241(procname(n-1)) ;
        end if;
    end proc: # R. J. Mathar, May 06 2017

Formula

a(n+1) = A208241(a(n)). - Reinhard Zumkeller, Feb 14 2013

A048551 p(n+1) is next smallest prime beginning with p(n), initial prime is 5.

Original entry on oeis.org

5, 53, 5303, 530303, 53030317, 530303173, 53030317313, 530303173133, 53030317313327, 53030317313327047, 5303031731332704703, 530303173133270470327, 5303031731332704703273, 530303173133270470327321
Offset: 0

Views

Author

Patrick De Geest, May 15 1999

Keywords

Crossrefs

A048554 p(n+1) is next smallest prime beginning with p(n), initial prime is 13.

Original entry on oeis.org

13, 131, 1319, 131909, 13190909, 1319090933, 131909093341, 13190909334101, 1319090933410141, 131909093341014131, 13190909334101413129, 131909093341014131297, 13190909334101413129739
Offset: 0

Views

Author

Patrick De Geest, May 15 1999

Keywords

Crossrefs

A051670 Smallest prime that concatenated with all previous terms of sequence forms a prime.

Original entry on oeis.org

2, 3, 3, 3, 3, 23, 7, 3, 53, 19, 149, 571, 3, 131, 3, 151, 389, 31, 389, 97, 59, 277, 491, 181, 59, 67, 647, 1117, 797, 433, 41, 367, 29, 487, 719, 283, 347, 97, 1103, 193, 821, 13, 29, 31, 947, 619, 167, 229, 479, 271, 1217, 79, 2777, 241, 1361, 751, 83, 4603, 317
Offset: 1

Views

Author

Felice Russo, Dec 15 1999

Keywords

Examples

			The 6th term of the sequence is 23 because that is smallest prime that when concatenated with previous terms 2, 3, 3, 3, 3, produces a prime (2333323).
		

References

  • A. Murthy, Smar. Notions J. Vol. 11, N. 1-2-3 Spring 2000

Crossrefs

Cf. A048549 and A083758.

Programs

  • Mathematica
    nxt[{lst_,n_}]:=Module[{id=IntegerDigits[lst],np=2},While[ !PrimeQ[ FromDigits[ Join[id, IntegerDigits[np]]]],np=NextPrime[np]];{FromDigits[ Join[id,IntegerDigits[np]]],np}]; Transpose[NestList[nxt,{2,2},60]] [[2]] (* Harvey P. Dale, May 25 2015 *)
    nxt[{l_,a_}]:=Module[{k=2},While[CompositeQ[l*10^IntegerLength[k]+ k],k= NextPrime[ k]];{l*10^IntegerLength[k]+k,k}]; NestList[nxt,{2,2},60][[All,2]] (* Harvey P. Dale, Aug 09 2020 *)

Extensions

Extended by T. D. Noe, May 01 2010

A100893 a(n) = smallest n-digit prime formed by appending a digit to a(n-1); a(1) = 2.

Original entry on oeis.org

2, 23, 233, 2333, 23333
Offset: 1

Views

Author

Jorge Coveiro, Jan 10 2005

Keywords

Comments

This sequence is finite because there is no prime a(6) since 233331,233333,233337,233339 are not prime.
This is an initial subsequence of A048549, A065122, A088603, and A127889; and for any b, the base b analog of this sequence is an initial subsequence of the base b analog of each of these three sequences. [From Franklin T. Adams-Watters, Jun 27 2009]

Examples

			a(1)=2
a(2)=23
a(3)=233
a(4)=2333
a(5)=23333
		
Showing 1-10 of 12 results. Next