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 1-3 of 3 results.

A061479 Smallest number m such that first digit - second digit + third digit - fourth digit ... (of m) = n.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 109, 209, 309, 409, 509, 609, 709, 809, 909, 10909, 20909, 30909, 40909, 50909, 60909, 70909, 80909, 90909, 1090909, 2090909, 3090909, 4090909, 5090909, 6090909, 7090909, 8090909, 9090909, 109090909, 209090909
Offset: 0

Views

Author

Amarnath Murthy, May 05 2001

Keywords

Examples

			a(14) = 509 as 5-0+9 =14 and it is the smallest such number.
		

Crossrefs

Programs

  • Mathematica
    m = 0; Do[ While[ a = IntegerDigits[ m ]; l = Length[ a ]; e = o = {}; Do[ o = Append[ o, a[ [ 2k - 1 ] ] ], {k, 1, l/2 + .5} ]; Do[ e = Append[ e, a[ [ 2k ] ] ], {k, 1, l/2} ]; Abs[ Apply[ Plus, o ] - Apply [ Plus, e ] ] != n, m++ ]; Print[ m ], {n, 1, 50} ]

Extensions

More terms from Robert G. Wilson v, May 10 2001

A236402 Numbers with property that the sum of any pair of adjacent digits is a substring of the number.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 400, 401, 402, 403, 404, 405, 406, 407
Offset: 1

Views

Author

Eric Angelini, Jan 30 2014

Keywords

Comments

This sequence has density 1, since all numbers except a thin fraction have digits 0 through 18 in base 100. In particular, there are at most x^0.99782 non-members up to x for large enough x. (This can be improved.) - Charles R Greathouse IV, Jan 30 2014
1263907548 is the smallest term that contains all ten digits. - M. F. Hasler, Jan 30 2014
Where does this first differ from A032945? - R. J. Mathar, Feb 03 2014
This first differs from A032945 at a(110)=910 (followed by 1000, 1001, 1002, ...) while A032945(110)=1000 (followed by 1010, 1020, 1030, ...). - M. F. Hasler, Dec 28 2014

Examples

			Examples of numbers in the sequence:
80 --> 8+0=8
107 --> 1+0=1  /  0+7=7
910 --> 9+1=10  /  1+0=1
1037 --> 1+0=1  /  0+3=3  /  3+7=10
1459 --> 1+4=5  /  4+5=9  /  5+9=14
41358 --> 4+1=5  /  1+3=4  /  3+5=8  /  5+8=13
		

Crossrefs

Cf. A236403 (complement).

Programs

  • Mathematica
    fQ[n_] := Module[{d, p, s}, d = IntegerDigits[n]; p = Partition[d, 2, 1]; s = Plus @@@ p; Complement[s, Union[d, FromDigits /@ p]] == {}]; Join[Range[0, 9], Select[Range[10, 1000], fQ]] (* T. D. Noe, Jan 30 2014 *)
  • PARI
    is(n)=my(d=digits(n),S=Set(d),v=List(),t); for(i=2,#d, listput(v, 10*d[i-1]+d[i])); S=Set(concat(S,Vec(v))); for(i=2,#d, t=d[i-1]+d[i]; if(!setsearch(S, t), return(0))); 1 \\ Charles R Greathouse IV, Jan 13 2015
    
  • Python
    def ok(n):
      s = str(n)
      return all(str(sum(map(int, s[i:i+2]))) in s for i in range(len(s)-1))
    print(list(filter(ok, range(408)))) # Michael S. Branicky, Jun 11 2021

Formula

a(n) ~ n. - Charles R Greathouse IV, Jan 30 2014

A252480 Numbers whose decimal representation has at least one '0' digit in a position other than the final digit.

Original entry on oeis.org

100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 600, 601, 602, 603, 604, 605, 606
Offset: 1

Views

Author

M. F. Hasler, Dec 28 2014

Keywords

Comments

Similar but different sequences are the "Cyclops numbers" A134808 and A032945 and A051022, which are subsequences, except for the 1- and 2-digit terms.
Also, numbers whose decimal representation cannot be split up between any two digits without producing a string with a leading zero (other than "0" itself).
Also, numbers n > 9 such that floor(n/10) is in A011540, i.e., has a digit '0'.

Programs

  • Mathematica
    Select[Range[10,700],DigitCount[Floor[#/10],10,0]>0&] (* Harvey P. Dale, May 10 2020 *)
  • PARI
    is(n)=n>9 && !vecmin(digits(n\10))
Showing 1-3 of 3 results.