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 1-5 of 5 results.

A038367 Numbers n with property that (product of digits of n) is divisible by (sum of digits of n).

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 22, 30, 36, 40, 44, 50, 60, 63, 66, 70, 80, 88, 90, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 120, 123, 130, 132, 138, 140, 145, 150, 154, 159, 160, 167, 170, 176, 180, 183, 189, 190, 195, 198, 200, 201, 202, 203
Offset: 1

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Author

Keywords

Comments

Equal to the disjoint union of A061013 and A011540 \ {0}. Contains in particular all positive single-digit integers, those with a digit 0, and 22*{1,...,18}. If x is in the sequence, any digit-permutation of x is also in the sequence. - M. F. Hasler, Feb 28 2018

Crossrefs

See A061013 for case where 0 digits are excluded. Cf. A055931.

Programs

  • Magma
    [0] cat [n: n in [1..250] | IsIntegral(&*Intseq(n)/&+Intseq(n))]; // Bruno Berselli, Feb 09 2016
    
  • Maple
    isA038367 := proc(n)
        if type( A007954(n)/A007953(n),'integer') then
            true;
         else
            false;
        end if;
    end proc :
    for n from 1 to 500 do
        if isA038367(n) then
            printf("%d,",n) ;
        end if;
    end do: # R. J. Mathar, Jun 30 2020
  • Mathematica
    okQ[n_]:=Module[{idn=IntegerDigits[n]},Divisible[Times@@idn,Total[idn]]]
    Select[Range[500],okQ] (* Harvey P. Dale, Nov 24 2010 *)
  • PARI
    is(n)=n&&prod(i=1,#n=digits(n),n[i])%vecsum(n)==0 \\ M. F. Hasler, Feb 28 2018

Extensions

Corrected by Vladeta Jovovic and Larry Reeves (larryr(AT)acm.org), Jun 08 2001
Erroneous 0 term removed by David A. Corneth, Jun 05 2016

A062045 Positive numbers whose product of digits is 12 times their sum.

Original entry on oeis.org

666, 1479, 1497, 1568, 1586, 1658, 1685, 1749, 1794, 1856, 1865, 1947, 1974, 2349, 2394, 2439, 2446, 2464, 2493, 2644, 2934, 2943, 3249, 3294, 3345, 3354, 3429, 3435, 3453, 3492, 3534, 3543, 3924, 3942, 4179, 4197, 4239, 4246, 4264, 4293, 4329, 4335, 4353, 4392
Offset: 1

Views

Author

Amarnath Murthy, Jun 28 2001

Keywords

Examples

			2349 belongs to the sequence as (2*3*4*9)/(2+3+4+9) = 216/18 = 12.
		

Crossrefs

Programs

  • Mathematica
    okQ[n_]:=Module[{idn=IntegerDigits[n]},Times@@idn/Total[idn]==12]
    Select[Range[10000],okQ] (* Harvey P. Dale, Nov 25 2010 *)
  • PARI
    isok(n) = my(d=digits(n)); vecprod(d)==12*vecsum(d) \\ Mohammed Yaseen, Sep 12 2022
    
  • Python
    from math import prod
    def ok(n): d = list(map(int, str(n))); return prod(d) == 12*sum(d)
    print([k for k in range(1, 4400) if ok(k)]) # Michael S. Branicky, Sep 12 2022

Extensions

Corrected and extended by Larry Reeves (larryr(AT)acm.org), Jul 06 2001
More terms from Harvey P. Dale, Nov 25 2010
Offset corrected by Mohammed Yaseen, Sep 12 2022

A064154 Numbers whose product of digits equals the number of digits times the sum of digits.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 36, 44, 63, 159, 167, 176, 195, 235, 253, 325, 333, 352, 519, 523, 532, 591, 617, 671, 716, 761, 915, 951, 1247, 1274, 1344, 1427, 1434, 1443, 1472, 1724, 1742, 2147, 2174, 2226, 2262, 2417, 2471, 2622, 2714, 2741, 3144, 3414
Offset: 1

Views

Author

Felice Russo, Sep 14 2001

Keywords

Comments

A subset of A061013.

Examples

			36 belongs to the sequence because 3*6 = 18 and 2*(3+6) = 18.
		

Crossrefs

Programs

  • Mathematica
    Select[Range[0, 3414], (d = IntegerDigits[#]; Times @@ d == Length[d] Plus @@ d) &] (* Giovanni Resta, Jun 25 2018 *)
  • PARI
    for(n=0,10000,my(v=digits(n));if(vecprod(v)==#v*vecsum(n),print1(n,", "))) \\ Derek Orr, Sep 09 2018

Extensions

Offset set to 1 by Giovanni Resta, Jun 25 2018

A126789 a(n) is the smallest number such that the product of its digits is n times the sum of its digits, or 0 if no such number exists.

Original entry on oeis.org

1, 36, 66, 88, 257, 268, 279, 448, 369, 459, 0, 666, 0, 578, 579, 678, 0, 1689, 0, 2558, 789, 0, 0, 1899, 13557, 0, 999, 3477, 0, 2589, 0, 2688, 0, 0, 13578, 3489, 0, 0, 0, 3588, 0, 2799, 0, 0, 4569, 0, 0, 4668, 4677, 5568, 0, 0, 0, 3699, 0, 3789, 0, 0, 0, 4599, 0, 0
Offset: 1

Views

Author

Tanya Khovanova, Feb 19 2007

Keywords

Comments

a(11) = 0. Proof: 11 is a prime number and the product of digits of a number in base 10 can never be a multiple of 11. - Stefan Steinerberger, Jun 07 2007
More generally, a(n) = 0 for all n which are divisible by a prime bigger than 7. This means that the sequence will almost always be 0 (with the set of exceptions having density 0). In each term the digits will be increasing (otherwise we could rearrange the digits so that they form a smaller number with the specified property). If no prime factors of n exceed 7, does this mean that a(n) is not 0? - Stefan Steinerberger, Jun 14 2007

Examples

			a(2)=36 because 3*6/(3+6) = 2 and no number smaller than 36 has this property.
		

Crossrefs

This sequence is a subsequence of A061013 (Product of digits of n) is divisible by (sum of digits of n), where 0's are not permitted.

Programs

  • Maple
    for n from 1 to 10 do b:=proc(k) local kk: kk:=convert(k,base,10): if product(kk[j],j=1..nops(kk))=n*sum(kk[j],j=1..nops(kk)) then k else fi end: a[n]:=[seq(b(k),k=1..1000)][1]: od: seq(a[n],n=1..10); # program works only for n from 1 to 10 Emeric Deutsch, Mar 07 2007
  • Mathematica
    a[1] := 1; a[n_] := Module[{}, k = 0; If[FactorInteger[n][[ -1, 1]] < 8, k = 1; While[Times @@ IntegerDigits[k] != n*Plus @@ IntegerDigits[k], k++ ]]; k]; Table[a[i], {i, 1, 80}] (* Stefan Steinerberger, Jun 14 2007 *)

Extensions

More terms from Emeric Deutsch, Mar 07 2007
More terms from Stefan Steinerberger, Jun 14 2007

A062519 Numbers for which (product of digits) / (sum of digits) is an integer > 1.

Original entry on oeis.org

36, 44, 63, 66, 88, 138, 145, 154, 159, 167, 176, 183, 189, 195, 198, 224, 235, 242, 246, 253, 257, 264, 268, 275, 279, 286, 297, 318, 325, 333, 345, 347, 352, 354, 357, 369, 374, 375, 381, 396, 415, 422, 426, 435, 437, 448, 451, 453, 456, 459, 462, 465
Offset: 1

Views

Author

Amarnath Murthy, Jun 26 2001

Keywords

Examples

			63 is a member as (6*3)/(6+3) = 2 > 1.
		

Crossrefs

Sequence A061013 allows product = sum.

Programs

  • Mathematica
    pdsdQ[n_]:=Module[{idn=IntegerDigits[n],r},r=Times@@idn/Total[idn];IntegerQ[ r]&&r>1]; Select[Range[500],pdsdQ] (* Harvey P. Dale, Dec 22 2019 *)
  • PARI
    ok(n)={my(d=digits(n), p=vecprod(d), s=vecsum(d)); p > s && p%s == 0} \\ Andrew Howroyd, Sep 17 2024

Extensions

Corrected and extended by Larry Reeves (larryr(AT)acm.org), Jun 29 2001
Offset changed by Andrew Howroyd, Sep 17 2024
Showing 1-5 of 5 results.