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.

A062115 Numbers with no prime substring in their decimal expansion.

Original entry on oeis.org

0, 1, 4, 6, 8, 9, 10, 14, 16, 18, 40, 44, 46, 48, 49, 60, 64, 66, 68, 69, 80, 81, 84, 86, 88, 90, 91, 94, 96, 98, 99, 100, 104, 106, 108, 140, 144, 146, 148, 160, 164, 166, 168, 169, 180, 184, 186, 188, 400, 404, 406, 408, 440, 444, 446, 448, 460, 464, 466
Offset: 1

Views

Author

Erich Friedman, Jun 28 2001

Keywords

Comments

This is a 10-automatic sequence, a consequence of the finitude of A071062. - Charles R Greathouse IV, Sep 27 2011
Subsequence of A202259 (right-truncatable nonprimes). Supersequence of A202262 (composite numbers in which all substrings are composite), A202265 (nonprime numbers in which all substrings and reversal substrings are nonprimes). - Jaroslav Krizek, Jan 28 2012

Examples

			25 is not included because 5 is prime.
		

Crossrefs

Subsequence of A084984. [Arkadiusz Wesolowski, Jul 05 2011]
Cf. A071062.
Cf. A163753 (complement).

Programs

  • Haskell
    a062115 n = a062115_list !! (n-1)
    a062115_list = filter ((== 0) . a039997) a084984_list
    -- Reinhard Zumkeller, Jan 31 2012
    
  • Python
    from sympy import isprime
    def ok(n):
        s = str(n)
        ss = (int(s[i:j]) for i in range(len(s)) for j in range(i+1, len(s)+1))
        return not any(isprime(k) for k in ss)
    print([k for k in range(500) if ok(k)]) # Michael S. Branicky, May 02 2023
    
  • Python
    # faster for initial segment of sequence; uses ok, import above
    from itertools import chain, count, islice, product
    def agen(): # generator of terms
        yield from chain((0,), (int(t) for t in (f+"".join(r) for d in count(1) for f in "14689" for r in product("014689", repeat=d-1)) if ok(t)))
    print(list(islice(agen(), 100))) # Michael S. Branicky, May 02 2023

Formula

A039997(a(n)) = 0. - Reinhard Zumkeller, Jul 16 2007
From Charles R Greathouse IV, Mar 23 2010: (Start)
a(n) = O(n^(log_4 10)) = O(n^1.661) because numbers containing only 0,4,6,8 are in this sequence.
a(n) = Omega(n^(log_13637 1000000)) = Omega(n^1.451) for similar reasons; this bound can be increased by considering longer sequences of digits. (End)

Extensions

Offset corrected by Arkadiusz Wesolowski, Jul 27 2011

A202259 Right-truncatable nonprimes: every prefix is nonprime number.

Original entry on oeis.org

0, 1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 40, 42, 44, 45, 46, 48, 49, 60, 62, 63, 64, 65, 66, 68, 69, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 102, 104, 105, 106, 108, 120, 121, 122, 123, 124, 125, 126, 128, 129, 140, 141, 142
Offset: 1

Views

Author

Jaroslav Krizek, Dec 25 2011

Keywords

Comments

Supersequence of A202260, A202265. - Barry Carter, Sep 16 2016

Crossrefs

Cf. A012883 (right-truncatable noncomposites), A024770 (right-truncatable primes), A202260 (right-truncatable composites).

Programs

  • Maple
    filter:= proc(n) option remember; not isprime(n) and procname(floor(n/10)) end proc:
    for i from 0 to 9 do filter(i):= not isprime(i) od:
    select(filter, [$0..1000]); # Robert Israel, Nov 01 2016

A202262 Composite numbers in which all substrings are composite.

Original entry on oeis.org

4, 6, 8, 9, 44, 46, 48, 49, 64, 66, 68, 69, 84, 86, 88, 94, 96, 98, 99, 444, 446, 448, 464, 466, 468, 469, 484, 486, 488, 494, 496, 498, 644, 646, 648, 649, 664, 666, 668, 669, 684, 686, 688, 694, 696, 698, 699, 844, 846, 848, 849, 864, 866, 868, 869, 884, 886
Offset: 1

Views

Author

Jaroslav Krizek, Dec 25 2011

Keywords

Comments

Subsequence of A062115, A202260, A029581.
Supersequence of A202265.
This is a 10-automatic sequence, see A071062. - Charles R Greathouse IV, Jan 01 2012

Crossrefs

Cf. A085823 (primes in which all substrings are primes), A068669 (noncomposite numbers in which all substrings are noncomposite), A062115 (nonprimes in which all substrings are nonprimes).
Cf. A010051.

Programs

  • Mathematica
    sub[n_] := Block[{d = IntegerDigits[n]}, Union@ Reap[ Do[Sow@ FromDigits@ Take[d, {i, j}], {j, Length@ d}, {i, j}]][[2, 1]]]; Select[ Range@ 900, Union[{4, 6, 8, 9}, IntegerDigits[#]] == {4, 6, 8, 9} && AllTrue[sub[#], CompositeQ] &] (* Giovanni Resta, Dec 20 2019 *)
  • PARI
    See Links section.

Extensions

Data corrected by Reinhard Zumkeller, May 05 2012
Data corrected by Rémy Sigrist, Dec 19 2019
Incorrect Haskell program deleted by M. F. Hasler, Dec 20 2019

A202263 Primes in which all substrings and reversal substrings are primes.

Original entry on oeis.org

2, 3, 5, 7, 37, 73, 373
Offset: 1

Views

Author

Jaroslav Krizek, Dec 25 2011

Keywords

Comments

Sequence is finite with 7 terms.
Subsequence of A085823, A068669, A024770, A012883.

Examples

			All substrings and reversal substrings of 373 are primes:3, 7, 37, 73, 373.
		

Crossrefs

Cf. A202264 (noncomposite numbers in which all substrings and reversal substrings are noncomposite), A202265 (nonprimes in which all substrings and reversal substrings are nonprimes), A202266 (composite numbers in which all substrings and reversal substrings are composites).

A202266 Composite numbers in which all substrings and reversal substrings are composites.

Original entry on oeis.org

4, 6, 8, 9, 44, 46, 48, 49, 64, 66, 68, 69, 84, 86, 88, 94, 96, 99, 444, 446, 448, 464, 466, 468, 469, 484, 486, 488, 494, 496, 644, 646, 648, 649, 664, 666, 668, 669, 684, 686, 688, 694, 696, 699, 844, 846, 848, 849, 864, 866, 868, 869, 884, 886, 888, 946, 948
Offset: 1

Views

Author

Jaroslav Krizek, Dec 25 2011

Keywords

Comments

Subsequence of A202265, A202262.

Examples

			All substrings and reversal substrings of 446 are composites: 4, 6, 44, 46, 64, 446, 644.
		

Crossrefs

Cf. A202263 (primes in which all substrings and reversal substrings are primes), A202264 (noncomposite numbers in which all substrings and reversal substrings are noncomposite), A202265 (nonprimes in which all substrings and reversal substrings are nonprimes).

A202264 Noncomposite numbers in which all substrings and reversal substrings are noncomposites.

Original entry on oeis.org

1, 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 113, 131, 311, 313, 373
Offset: 1

Views

Author

Jaroslav Krizek, Dec 25 2011

Keywords

Comments

Sequence is finite with 17 terms.
Supersequence of A202263, A085823.
Subsequence of A068669, A012883, A024770, A012883.

Examples

			All substrings and reversal substrings of 311 are noncomposites: 1, 3, 11, 13, 31, 113, 311.
		

Crossrefs

Cf. A202263 (primes in which all substrings and reversal substrings are primes), A202265 (nonprimes in which all substrings and reversal substrings are nonprimes), A202266 (composite numbers in which all substrings and reversal substrings are composites).
Showing 1-6 of 6 results.