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 17 results. Next

A069675 Primes all of whose internal digits (if any) are 0.

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, 307, 401, 409, 503, 509, 601, 607, 701, 709, 809, 907, 1009, 2003, 3001, 4001, 4003, 4007, 5003, 5009, 6007, 7001, 8009, 9001, 9007, 10007, 10009
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Comments

Despite their initial density, these primes are rare. The value of a(310) = 9*10^2914 + 7. Beginning with a(54), this is a subsequence of A164968. Indeed, these could be called the "naughtiest" primes. - Harlan J. Brothers, Aug 17 2015
There are expected to be infinitely many terms, but growing very rapidly, something like a(n) ~ exp(exp(const * n)). - Robert Israel, Aug 17 2015

Examples

			4001 is in the sequence because it is prime and all the internal digits (the digits between 4 and 1) are zero. - _Michael B. Porter_, Aug 11 2016
		

Crossrefs

Programs

  • Maple
    A := {}:
    for n to 1000 do
      p := ithprime(n):
      d := convert(p, base, 10):
      s := 0:
      for m from 2 to nops(d)-1 do
        s := s+d[m]:
      end do
      if s = 0 then
        A := `union`(A, {p})
      end if:
    end do:
    A := A
    # César Eliud Lozada, Sep 04 2012
    select(isprime, [$1..9, seq(seq(seq(10^d*a+b, b=1..9),a=1..9), d=1..10)]); # Robert Israel, Aug 18 2015
  • Mathematica
    Select[Prime[Range[1, 100000]], IntegerLength[#] < 3 || Union@Rest@Most@IntegerDigits[#, 10] == {0} &] (* Harlan J. Brothers, Aug 17 2015 *)
    Select[Join[Range[1, 99], Flatten[Table[a*10^d + b, {d, 2, 50}, {a, 1, 9}, {b, 1, 9}]]], PrimeQ[#] &] (* Seth A. Troisi, Aug 03 2016 *)
  • PARI
    go(n)=my(v=List(primes(4)),t); for(d=1,n-1, for(i=1,9, forstep(j=1,9,[2,4,2], if(isprime(t=10^d*i+j), listput(v,t))))); Vec(v) \\ Charles R Greathouse IV, Sep 14 2015
    
  • Python
    from sympy import isprime
    print([2, 3, 5, 7] + list(filter(isprime, (a*10**d+b for d in range(1, 101) for a in range(1, 10) for b in [1, 3, 7, 9])))) # Michael S. Branicky, May 08 2021

Formula

a(n) >> 10^(n/24). - Charles R Greathouse IV, Sep 14 2015

Extensions

Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069676 Primes with either no internal digits or all internal digits are 1.

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, 113, 211, 311, 313, 317, 419, 613, 617, 619, 719, 811, 911, 919, 1117, 2111, 2113, 3119, 4111, 5113, 5119, 6113, 8111, 8117, 11113, 11117, 11119, 41113, 41117, 71119
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Programs

  • Mathematica
    aid1Q[n_]:=Union[Most[Rest[IntegerDigits[n]]]]=={1}; Join[Prime[Range[PrimePi[ 100]]], Select[Prime[Range[PrimePi[100]+1,7100]],aid1Q]] (* Harvey P. Dale, Apr 12 2013 *)
  • PARI
    lista(na) = my(vp = List(primes(primepi(100)))); for (n=1, na, my(x=(10^n-1)/9); for (i=1, 9, forstep(j=1, 9, 2, my(y=10^(n+1)*i + 10*x + j); if (ispseudoprime(y), listput(vp, y));););); Vec(vp); \\ Michel Marcus, Jul 12 2022

Extensions

Corrected by Ray Chandler, Nov 24 2003
Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069677 Primes with either no internal digits or all internal digits are 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, 127, 223, 227, 229, 421, 521, 523, 727, 821, 823, 827, 829, 929, 1223, 1229, 2221, 3221, 3229, 4229, 5227, 6221, 6229, 7229, 8221, 9221, 9227, 12227, 22229, 42221
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Programs

  • Mathematica
    Join[Prime[Range[25]],Select[Prime[Range[26,4500]],Union[Most[ Rest[ IntegerDigits[ #]]]] =={2}&]] (* Harvey P. Dale, Aug 12 2021 *)
  • PARI
    uptoqdigits(n) = { my(ld = [1,3,7,9]); n = max(n, 2); res = List(primes(primepi(97))); for(i = 1, n-2, twos = 20*(10^i\9); for(j = 1, 9, for(k = 1, #ld, c = j*10^(i+1) + twos + ld[k]; if(isprime(c), listput(res, c) ) ) ) ); Set(res) } \\ David A. Corneth, Aug 12 2021
    
  • Python
    from sympy import isprime
    def agen(maxdigits):
        yield from [2, 3, 5, 7]
        for d in range(2, maxdigits+1):
            pow10, mid = 10**(d-1), 0 if d < 3 else 10*int('2'*(d-2))
            cands = (a*pow10+mid+b for a in range(1, 10) for b in [1, 3, 7, 9])
            yield from filter(isprime, cands)
    print([an for an in agen(100)]) # Michael S. Branicky, Aug 12 2021

Extensions

Corrected by Ray Chandler, Nov 24 2003
Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069678 Primes with either no internal digits or all internal digits are 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, 131, 137, 139, 233, 239, 331, 337, 431, 433, 439, 631, 733, 739, 839, 937, 2333, 2339, 3331, 4337, 4339, 5333, 6337, 7331, 7333, 9337, 13331, 13337, 13339, 23333, 23339
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Programs

  • Mathematica
    Join[Prime[Range[25]],Select[Flatten[Table[10FromDigits[PadRight[{n},k,3]]+d,{n,9},{d,{1,3,7,9}},{k,2,5}]],PrimeQ]]//Sort (* Harvey P. Dale, Aug 08 2020 *)

Extensions

Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069679 Primes with either no internal digits or all internal digits are 4.

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, 149, 241, 347, 349, 443, 449, 541, 547, 641, 643, 647, 743, 941, 947, 1447, 2441, 2447, 3449, 4441, 4447, 5441, 5443, 5449, 6449, 8443, 8447, 14447, 14449, 24443, 44449
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Programs

  • Mathematica
    Join[Prime[Range[25]],Select[Prime[Range[26,5000]],Union[Most[Rest[ IntegerDigits[ #]]]] =={4}&]] (* Harvey P. Dale, Dec 08 2022 *)

Extensions

Corrected by Ray Chandler, Nov 24 2003
Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069680 Primes with either no internal digits or all internal digits are 5.

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, 151, 157, 251, 257, 353, 359, 457, 557, 653, 659, 751, 757, 853, 857, 859, 953, 1553, 1559, 2551, 2557, 3557, 3559, 5557, 6551, 6553, 7559, 9551, 15551, 15559, 45553
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Extensions

Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069681 Primes with either no internal digits or all internal digits are 6.

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, 163, 167, 263, 269, 367, 461, 463, 467, 563, 569, 661, 761, 769, 863, 967, 1663, 1667, 1669, 2663, 4663, 5669, 6661, 7669, 8663, 8669, 9661, 16661, 26669, 46663, 56663
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Extensions

Corrected by Ray Chandler, Nov 24 2003
Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069682 Primes with either no internal digits or all internal digits are 7.

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, 173, 179, 271, 277, 373, 379, 479, 571, 577, 673, 677, 773, 877, 971, 977, 1777, 2777, 3779, 5779, 6779, 8779, 27773, 27779, 47777, 47779, 57773, 67777, 77773, 97771
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Extensions

Corrected by Ray Chandler, Nov 24 2003
Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069683 Primes with either no internal digits or all internal digits are 8.

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, 181, 281, 283, 383, 389, 487, 587, 683, 787, 881, 883, 887, 983, 1889, 2887, 3881, 3889, 4889, 5881, 6883, 7883, 8887, 9883, 9887, 48883, 48889, 58889, 68881, 78887
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Crossrefs

Extensions

Corrected by Ray Chandler, Nov 24 2003
Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011

A069693 Triangular numbers with either no internal digits or all internal digits are 0.

Original entry on oeis.org

0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 300, 406, 703, 903, 3003, 4005, 8001
Offset: 1

Views

Author

Amarnath Murthy, Apr 06 2002

Keywords

Examples

			The internal digits of 3003 are "00", which are both 0. 15 has no internal digits.
		

Crossrefs

Programs

  • Mathematica
    Do[ If[ Union[ Drop[ RotateLeft[ IntegerDigits[n(n + 1)/2]], -2]] == {0}, Print[n(n + 1)/2]], {n, 14, 2 10^6}]

Extensions

Corrected by Sascha Kurz, Jan 02 2003
Showing 1-10 of 17 results. Next