login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A091784 Numbers n with digits in nondecreasing order such that sum of the reciprocal of digits is an integer. 2
1, 11, 22, 111, 122, 236, 244, 333, 1111, 1122, 1236, 1244, 1333, 2222, 2488, 2666, 3366, 3446, 4444, 11111, 11122, 11236, 11244, 11333, 12222, 12488, 12666, 13366, 13446, 14444, 22236, 22244, 22333, 26999, 28888, 33999, 34688, 36666, 44488, 44666, 55555, 111111, 111122 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

236 is a member and 263, 326, 362, 623, 632 which are digit permutations of 236 are not included (unlike A037268). Subsidiary sequences: (1) Sum of the reciprocals of all n-digit members. (2) Let the terms with reciprocal sum n be arranged in nondecreasing order. (i) The n-th term in the above sequence (2). (ii) The number of digits in this term of (i).

Subsequence of A009994. - David A. Corneth, Sep 05 2016

LINKS

Harvey P. Dale and David A. Corneth, Table of n, a(n) for n = 1..10001 (First 237 terms from Harvey P. Dale)

EXAMPLE

236 is a member as 1/2 + 1/3 +1/6 = 1.

MATHEMATICA

Do[l = IntegerDigits[n]; If[Intersection[l, {0}] == {} && IntegerQ[Plus @@ Map[(1/#)&, l]] && Sort[l] == l, Print[n]], {n, 1, 10^5}] (* Ryan Propper, Aug 27 2005 *)

Select[Range[50000], Min[Differences[IntegerDigits[#]]]>=0&&IntegerQ[ Total[ 1/IntegerDigits[#]]]&] (* Harvey P. Dale, Aug 22 2016 *)

PROG

(PARI) is(n)=my(d=digits(n), v=vecsort(d), s); if(d==v, s=sum(i=1, #d, 1/d[i]); s==s\1, 0) \\ David A. Corneth, Sep 06 2016

(PARI) getNDigitTerms(n)=my(v=List(), t); forvec(x=vector(8, i, [0, n]), my(u=vector(n, i, 1), X=concat(x, n)); for(i=2, 9, for(j=X[i-1]+1, X[i], u[j]=i)); if(denominator(sum(i=1, #u, 1/u[i]))==1, listput(v, fromdigits(u))), 1); Set(v) \\ Charles R Greathouse IV, Sep 06 2016

CROSSREFS

Cf. A009994, A037268, A034708.

Sequence in context: A081930 A143964 A034708 * A213972 A061852 A083511

Adjacent sequences:  A091781 A091782 A091783 * A091785 A091786 A091787

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Feb 17 2004

EXTENSIONS

More terms from Ryan Propper, Aug 27 2005

Name corrected by David A. Corneth, Sep 05 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 17 03:42 EDT 2021. Contains 347478 sequences. (Running on oeis4.)