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.

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A384955 a(n) is the multinomial coefficient of the digits of n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 1, 4, 10, 20, 35, 56, 84, 120, 165, 220, 1, 5, 15, 35, 70, 126, 210, 330, 495, 715, 1, 6, 21, 56, 126, 252, 462, 792, 1287, 2002, 1, 7, 28, 84, 210, 462, 924, 1716, 3003, 5005
Offset: 0

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Author

Stefano Spezia, Jun 13 2025

Keywords

Examples

			a(35) = (3+5)!/(3!*5!) = 40320/(6*120) = 56;
a(1512) = (1+5+1+2)!/(1!*5!*1!*2!) = 362880/(120*2) = 1512.
		

Crossrefs

Programs

  • Maple
    a:= n-> (l-> combinat[multinomial](add(i,i=l), l[]))(convert(n, base, 10)):
    seq(a(n), n=0..69);  # Alois P. Heinz, Jun 15 2025
  • Mathematica
    a[n_]:=Multinomial @@IntegerDigits[n]; Array[a,70,0]
  • Python
    from math import factorial, prod
    def a(n): return factorial(sum(digits:=list(map(int, str(n))))) // prod(factorial(x) for x in digits)
    print([a(n) for n in range(70)]) # David Radcliffe, Jun 15 2025

Formula

a(n) = A269221(n)/A066459(n).
a(n) = 1 iff n is equal to 0 or has only one nonzero digit (cf. A037124).
Conjecture: a(n) = n iff n = 1 or n = 1512.

A071061 Abjad values of the Arabic letters in the traditional order for abjad calculations.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000
Offset: 1

Views

Author

Koksal Karakus (karakusk(AT)hotmail.com), May 26 2002

Keywords

Comments

The Greek or Ionian numerals are similar, but omit 1000. - Charles R Greathouse IV, Jun 25 2012

Crossrefs

Subsequence of A037124.
Cf. A051596.

A243079 Numbers n such that A = n - DigitProd(n) is divisible by the largest power of 10 <= A.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 35, 55, 62, 64, 66, 68, 75, 95, 236, 315, 324, 575, 612, 828, 935, 944, 4384, 5175, 7688, 7735, 8128, 8672, 9135, 9144, 9575, 91575
Offset: 1

Views

Author

Derek Orr, May 30 2014

Keywords

Comments

Trivially numbers in A037124 satisfy this but are not contained in this sequence.

Examples

			35-3*5 = 20 is divisible by the highest power of 10 below it (10^1). So 20 is a member of this sequence.
		

Crossrefs

Programs

  • PARI
    DP(n)={p=1; d=digits(n); for(i=1, #d, p*=d[i]); return(p)}
    for(k=1,10^7,if(n%10!=0&&(n-DP(n))%(10^(#Str(n-DP(n))-1))==0,print1(n,", ")))

A380818 Numbers k such that the Diophantine equation d_r*x^r + ... + d_0*x^0 = 0 has an integer solution. k = (d_r .. d_0) in decimal notation, d_i are the digits of k.

Original entry on oeis.org

0, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 33, 36, 39, 40, 44, 48, 50, 55, 60, 66, 70, 77, 80, 88, 90, 99, 100, 110, 120, 121, 130, 132, 140, 143, 144, 150, 154, 156, 160, 165, 168, 169, 170, 176, 180, 187, 190, 198, 200, 210, 220, 230, 231, 240, 242, 250
Offset: 1

Views

Author

Ctibor O. Zizka, Feb 04 2025

Keywords

Comments

For r >= 1, d_r >= 1, numbers k = d_r*10^r are terms. It looks like the solution x (if it exists) is from [-9, 0].

Examples

			k = 68: the Diophantine equation 6*x + 8 = 0 has no integer solution, thus k = 68 is not a term.
k = 132: the Diophantine equation 1*x^2 + 3*x + 2 = 0 has integer solutions x = -1, x = -2, thus k = 132 is a term.
		

Crossrefs

Cf. A037124 (for k >= 10).
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