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 30 results. Next

A095219 First differences of A053067.

Original entry on oeis.org

22, 433, 78454, 1112052505, 160606060606, 22070707070707, 2908080808080808, 370909090909090909, 46101010101010101010, 5611111111111111111111, 671212121212121212121212, 79131313131313131313131313, 9293949517171716261615233314205014, 106107108099816161515133215015015015015015015
Offset: 2

Views

Author

Amarnath Murthy, Jun 10 2004

Keywords

Examples

			a(2) = 456 - 23 = 433.
		

Programs

  • Maple
    A000124 := proc(n) n*(n+1)/2+1 ; end proc:
    catL := proc(L) local a; a := op(1,L) ; for i from 2 to nops(L) do a := cat2(a,op(i,L)) ; end do; a; end proc:
    A053067 := proc(n) local l ; l := A000124(n-1) ; catL([seq(k,k=l..l+n-1)]) ; end proc:
    A095219 := proc(n) A053067(n+1)-A053067(n) ; end proc:
    seq(A095219(n),n=1..15) ; # R. J. Mathar, Oct 14 2010

Extensions

Definition clarified by R. J. Mathar, Oct 14 2010

A133013 Concatenation of next n primes.

Original entry on oeis.org

2, 35, 71113, 17192329, 3137414347, 535961677173, 79838997101103107, 109113127131137139149151, 157163167173179181191193197, 199211223227229233239241251257, 263269271277281283293307311313317
Offset: 1

Views

Author

Omar E. Pol, Oct 19 2007

Keywords

Crossrefs

Cf. A053067, A053068. Prime numbers: A000040.

Programs

  • Mathematica
    With[{nn=15},FromDigits[Flatten[IntegerDigits/@#]]&/@TakeList[Prime[ Range[ (nn(nn+1))/2]],Range[nn]]] (* Requires Mathematica version 11 or later *) (* Harvey P. Dale, Apr 26 2018 *)

A035333 Concatenation of two or more consecutive positive integers.

Original entry on oeis.org

12, 23, 34, 45, 56, 67, 78, 89, 123, 234, 345, 456, 567, 678, 789, 910, 1011, 1112, 1213, 1234, 1314, 1415, 1516, 1617, 1718, 1819, 1920, 2021, 2122, 2223, 2324, 2345, 2425, 2526, 2627, 2728, 2829, 2930, 3031, 3132, 3233, 3334, 3435, 3456, 3536, 3637, 3738
Offset: 1

Views

Author

Keywords

Crossrefs

For concatenations of exactly k consecutive integers see A000027 (k=1), A127421 (k=2), A001703 (k=3), A279204 (k=4).
See also A007908 for concatenation of 1 through n.
For primes see A052087.
All of A007908, A052087, A053067, A279610 are subsequences.

Programs

  • Python
    import heapq
    from itertools import islice
    def agen():
        c = 12
        h = [(c, 1, 2)]
        nextcount = 3
        while True:
            (v, s, l) = heapq.heappop(h)
            yield v
            if v >= c:
                c = int(str(c) + str(nextcount))
                heapq.heappush(h, (c, 1, nextcount))
                nextcount += 1
            l += 1; v = int(str(v)[len(str(s)):] + str(l)); s += 1
            heapq.heappush(h, (v, s, l))
    print(list(islice(agen(), 47))) # Michael S. Branicky, Dec 23 2021

Extensions

Edited by Charles R Greathouse IV, Apr 28 2010
Corrected by Paul Tek, Jun 08 2013

A080480 Largest number formed by using all the digits (with multiplicity) of next n numbers.

Original entry on oeis.org

1, 32, 654, 98710, 5432111111, 987622111110, 87654322222222, 9654333333332210, 987544444443333210, 98765555555444443210, 9876666666665555543210, 988777777777776666543210, 99998888888888877654321100, 9999999998765544332211111110000000
Offset: 1

Views

Author

Amarnath Murthy, Mar 11 2003

Keywords

Examples

			a(4) = 98710 formed by using digits of 7,8,9 and 10.
		

Crossrefs

Cf. A053067 (next n concatenated), A076068 (smallest without zeros), A080479 (smallest).

Programs

  • Mathematica
    FromDigits[Sort[Flatten[IntegerDigits/@#],Greater]]&/@Table[ Reverse[ Range[ (n(n+1))/2+1,((n+1)(n+2))/2]],{n,0,15}] (* Harvey P. Dale, May 13 2017 *)
  • Python
    def a(n):
      s = "".join(sorted("".join(map(str, range((n-1)*n//2+1, n*(n+1)//2+1)))))
      return int("".join(sorted(s, reverse=True)))
    print([a(n) for n in range(1, 15)]) # Michael S. Branicky, Jan 23 2021

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 19 2003
More terms from Harvey P. Dale, May 13 2017

A080479 Smallest number formed by using all the digits (with multiplicity) of next n numbers.

Original entry on oeis.org

1, 23, 456, 10789, 1111112345, 101111226789, 22222222345678, 1022333333334569, 102333344444445789, 10234444455555556789, 1023455555666666666789, 102345666677777777777889, 10012345677888888888889999, 1000000011111122334455678999999999
Offset: 1

Views

Author

Amarnath Murthy, Mar 11 2003

Keywords

Crossrefs

Cf. A053067 (next n concatenated), A080480 (largest).

Programs

  • Python
    def a(n):
      s = "".join(sorted("".join(map(str, range((n-1)*n//2+1, n*(n+1)//2+1)))))
      if '0' not in s: return int(s)
      rz = s.rfind('0')
      return int(s[rz+1] + s[:rz+1] + s[rz+2:])
    print([a(n) for n in range(1, 15)]) # Michael S. Branicky, Jan 23 2021

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 19 2003

A076068 Smallest number that can be formed by using the nonzero digits of the numbers 1+n(n-1)/2 through n(n+1)/2.

Original entry on oeis.org

1, 23, 456, 1789, 1111112345, 11111226789, 22222222345678, 122333333334569, 12333344444445789, 1234444455555556789, 123455555666666666789, 12345666677777777777889, 112345677888888888889999, 111111122334455678999999999, 111111111111111111111111112234566778899
Offset: 1

Views

Author

Amarnath Murthy, Oct 05 2002

Keywords

Comments

Is there any r and s such that a(r) = a(s)? Probably not.

Examples

			a(4) = 1789 (=01789) formed by using digits of 7,8,9 and 10.
		

Crossrefs

Cf. A053067 (next n concatenated), A080479 (smallest with zeros), A080480 (largest with zeros).

Programs

  • Mathematica
    sncbf[n_]:=Sort[Flatten[IntegerDigits/@Range[(n(n-1))/2+1,(n(n+1))/2]]/.(0->Nothing)]//FromDigits; Array[sncbf,15] (* Harvey P. Dale, Nov 26 2019 *)
  • Python
    def a(n):
      s = "".join(sorted("".join(map(str, range((n-1)*n//2+1, n*(n+1)//2+1)))))
      if '0' not in s: return int(s)
      return int(s[s.rfind('0')+1:])
    print([a(n) for n in range(1, 16)]) # Michael S. Branicky, Jan 23 2021

Extensions

More terms from David Wasserman, Mar 19 2005

A133014 Concatenation of next n Mersenne primes.

Original entry on oeis.org

3, 731, 1278191131071, 52428721474836472305843009213693951618970019642690137449562111
Offset: 1

Views

Author

Omar E. Pol, Oct 19 2007

Keywords

Crossrefs

Cf. A053067, A053068. Mersenne primes: A000668.

A279610 a(n) = concatenate n consecutive integers, starting with the last number of the previous batch.

Original entry on oeis.org

1, 12, 234, 4567, 7891011, 111213141516, 16171819202122, 2223242526272829, 293031323334353637, 37383940414243444546, 4647484950515253545556, 565758596061626364656667, 67686970717273747576777879, 7980818283848586878889909192
Offset: 1

Views

Author

José de Jesús Camacho Medina, Dec 09 2016, and Paolo Iachia, Dec 15 2016

Keywords

Comments

A variant of A053067. The first number of the concatenation a(n) is A152947(n) = (n-2)*(n-1)/2+1 and the last is (n-1)*n/2+1.
The fourth term, 4567, is a prime. When is the next prime, if there is another? - N. J. A. Sloane, Dec 16 2016
a(n) is the concatenation of the terms of the n-th row of A122797 when seen as a triangle. - Michel Marcus, Dec 17 2016

Examples

			a(4) is the concatenation of 4 numbers beginning with the last number (4) that was used to build a(3), so a(4) = 4 5 6 7 = 4567. Then a(5) is the concatenation of 5 numbers beginning with the last number of a(4), which is 7, so a(5) = 7 8 9 10 11 = 7891011. And so on.
For n = 3, n^2/2 - n/2 + 1 = 4; a(3) = 4 + 3*10^1 + 2*10^(1+1) = 234.
		

Crossrefs

A subsequence of A035333. For primes in latter, see A052087.

Programs

  • Mathematica
    Table[FromDigits[Flatten[IntegerDigits /@ Range[(n(n - 1))/2 + 1, (n(n + 1))/2 + 1 ]]], {n, 0, 20}]
  • Python
    from _future_ import division
    def A279610(n):
        return int(''.join(str(d) for d in range((n-1)*(n-2)//2+1,n*(n-1)//2+2))) # Chai Wah Wu, Dec 17 2016

Formula

a(n) = n^2/2 - n/2 + 1 + Sum{k=1..n-1} ((n^2/2 - n/2 + 1 - k)*10^Sum{j=0..k-1} (floor(1+log_10(n^2/2 - n/2 + 1 - j)))).

A134800 Concatenation of next n partition numbers A000041.

Original entry on oeis.org

1, 12, 357, 11152230, 425677101135, 176231297385490627, 792100212551575195824363010, 37184565560468428349101431231014883, 179772163726015311853733844583531746326175175
Offset: 1

Views

Author

Omar E. Pol, Nov 12 2007

Keywords

Crossrefs

Cf. A000041, A053067, A132926, A133013. See A134801 for another version.

Programs

  • Mathematica
    FromDigits[Flatten[IntegerDigits/@#]]&/@With[{nn=10},TakeList[ PartitionsP[ Range[0,(nn(nn+1))/2]],Range[nn]]] (* Requires Mathematica version 11 or later *) (* Harvey P. Dale, Jul 25 2019 *)

Extensions

Edited by Charles R Greathouse IV, Apr 28 2010

A134801 Concatenation of next n partition numbers of positive integers.

Original entry on oeis.org

1, 23, 5711, 15223042, 5677101135176, 231297385490627792, 1002125515751958243630103718, 456556046842834910143123101488317977, 216372601531185373384458353174632617517589134
Offset: 1

Views

Author

Omar E. Pol, Nov 12 2007

Keywords

Crossrefs

Cf. A053067, A132926, A133013. Partition numbers: A000041. See A134800 for another version of the concatenation of next n partition numbers.

Programs

  • Mathematica
    Module[{nn=10},FromDigits[Flatten[IntegerDigits/@#]]&/@TakeList[ PartitionsP[ Range[ (nn(nn+1))/2]],Range[nn]]] (* Harvey P. Dale, Apr 18 2022 *)

Extensions

Edited by Charles R Greathouse IV, Apr 28 2010
Showing 1-10 of 30 results. Next