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 1-2 of 2 results.

A249515 Numbers k for which the digital sum of k contains the same distinct digits as k itself.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 199, 919, 991, 1188, 1818, 1881, 2999, 8118, 8181, 8811, 9299, 9929, 9992, 11177, 11444, 11717, 11771, 13333, 14144, 14414, 14441, 17117, 17171, 17711, 22888, 26666, 28288, 28828, 28882, 31333, 33133, 33313, 33331, 39999, 41144
Offset: 1

Views

Author

Jaroslav Krizek, Oct 31 2014

Keywords

Examples

			199 is in the sequence since 1 + 9 + 9 = 19.
		

Crossrefs

Programs

  • Magma
    [k: k in [0..1000000] | Set(Intseq(k)) eq Set(Intseq(&+Intseq(k)))];
    
  • Mathematica
    Select[Range[1000], Union[IntegerDigits[#]] == Union[Plus@@IntegerDigits[#]] &] (* Alonso del Arte, Nov 02 2014 *)
  • PARI
    for(n=0, 5*10^4, if(vecsort(digits(n),,8) ==vecsort(digits(sumdigits(n)),,8), print1(n,", "))) \\ Derek Orr, Nov 02 2014
    
  • Python
    from itertools import product
    A249515_list = [0]
    for g in range(1,12):
        xp, ylist = [], []
        for i in range(9*g,-1,-1):
            x = set(str(i))
            if not x in xp:
                xv = [int(d) for d in x]
                imin = int(''.join(sorted(str(i))))
                if max(xv)*(g-len(x)) >= imin-sum(xv) and i-sum(xv) >=  min(xv)*(g-len(x)):
                    xp.append(x)
                    for y in product(x,repeat=g):
                        if y[0] != '0' and set(y) == x and set(str(sum([int(d) for d in y]))) == x:
                            ylist.append(int(''.join(y)))
        A249515_list.extend(sorted(ylist)) # Chai Wah Wu, Nov 15 2014

A249517 Numbers k for which the digital sum A007953(k) and the digital product A007954(k) both contain the same distinct digits as the number k.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11111111111
Offset: 1

Views

Author

Jaroslav Krizek, Oct 31 2014

Keywords

Comments

a(12) = (10^106-1)/9 + 122222222. - Max Alekseyev, Nov 15 2014
Other entries include (10^111-1)/9, (10^113-1)/9 + 177, (10^115-1)/9 + 122222222, (10^117-1)/9 + 11117, (10^125-1)/9 + 2224, (10^126-1)/9 + 333335, (10^135-1)/9 + 4666, (10^143-1)/9 + 446, (10^143-1)/9 + 2224, (10^144-1)/9 + 33335. All other entries with 150 or fewer digits are formed by permutations of the decimal digits of these entries (including a(12)). (10^((10^m-1)/9)-1)/9 are entries of the sequence for m >= 0. - Chai Wah Wu, Nov 15 2014

Examples

			11111111111 is a term since A007953(11111111111) = 11 and A007954(11111111111) = 1.
		

Crossrefs

Intersection of A249515 and A249516. Subsequence of A249334.

Programs

  • Magma
    [0] cat [n: n in [0..10^7] | Set(Intseq(n)) eq Set(Intseq(&*Intseq(n))) and Set(Intseq(n)) eq Set(Intseq(&+Intseq(n)))];
    
  • PARI
    is(n)=if(n<=9,return(1)); my(d=digits(n),s=Set(d)); s==Set(digits(sum(i=1,#d,d[i]))) && s==Set(digits(prod(i=1,#d,d[i]))) \\ Charles R Greathouse IV, Nov 13 2014
    
  • Python
    from itertools import product
    from operator import mul
    from functools import reduce
    A249517_list = [0]
    for g in range(1,15):
        xp, ylist = [], []
        for i in range(9*g,-1,-1):
            x = set(str(i))
            if not (('0' in x) or (x in xp)):
                xv = [int(d) for d in x]
                imin = int(''.join(sorted(str(i))))
                if max(xv)*(g-len(x)) >= imin-sum(xv) and i-sum(xv) >=  min(xv)*(g-len(x)):
                    xp.append(x)
                    for y in product(x,repeat=g):
                        if set(y) == x:
                            yd = [int(d) for d in y]
                            if set(str(sum(yd))) == x == set(str(reduce(mul, yd, 1))):
                                ylist.append(int(''.join(y)))
        A249517_list.extend(sorted(ylist)) # Chai Wah Wu, Nov 15 2014

Extensions

a(11) = 11111111111 confirmed by Sean A. Irvine, Nov 13 2014, by direct search.
Showing 1-2 of 2 results.