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 1-4 of 4 results.

A059590 Numbers obtained by reinterpreting base-2 representation of n in the factorial base: a(n) = Sum_{k>=0} A030308(n,k)*A000142(k+1).

Original entry on oeis.org

0, 1, 2, 3, 6, 7, 8, 9, 24, 25, 26, 27, 30, 31, 32, 33, 120, 121, 122, 123, 126, 127, 128, 129, 144, 145, 146, 147, 150, 151, 152, 153, 720, 721, 722, 723, 726, 727, 728, 729, 744, 745, 746, 747, 750, 751, 752, 753, 840, 841, 842, 843, 846, 847, 848, 849, 864, 865
Offset: 0

Views

Author

Henry Bottomley, Jan 24 2001

Keywords

Comments

Numbers that are sums of distinct factorials (0! and 1! not treated as distinct).
Complement of A115945; A115944(a(n)) > 0; A115647 is a subsequence. - Reinhard Zumkeller, Feb 02 2006
A115944(a(n)) = 1. - Reinhard Zumkeller, Dec 04 2011
From Tilman Piesk, Jun 04 2012: (Start)
The inversion vector (compare A007623) of finite permutation a(n) (compare A055089, A195663) has only zeros and ones. Interpreted as a binary number it is 2*n (or n when the inversion vector is defined without the leading 0).
The inversion set of finite permutation a(n) interpreted as a binary number (compare A211362) is A211364(n).
(End)

Examples

			128 is in the sequence since 5! + 3! + 2! = 128.
a(22) = 128. a(22) = a(6) + (1 + floor(log(16) / log(2)))! = 8 + 5! = 128. Also, 22 = 10110_2. Therefore, a(22) = 1 * 5! + 0 * 4! + 1 * 3! + 1 + 2! + 0 * 0! = 128. - _David A. Corneth_, Aug 21 2016
		

Crossrefs

Indices of zeros in A257684.
Cf. A275736 (left inverse).
Cf. A025494, A060112 (subsequences).
Subsequence of A060132, A256450 and A275804.
Other sequences that are built by replacing 2^k in the binary representation with other numbers: A029931 (naturals), A089625 (primes), A022290 (Fibonacci), A197433 (Catalans), A276091 (n*n!), A275959 ((2n)!/2). Cf. also A276082 & A276083.

Programs

  • Haskell
    import Data.List (elemIndices)
    a059590 n = a059590_list !! n
    a059590_list = elemIndices 1 $ map a115944 [0..]
    -- Reinhard Zumkeller, Dec 04 2011
    
  • Maple
    [seq(bin2facbase(j),j=0..64)]; bin2facbase := proc(n) local i; add((floor(n/(2^i)) mod 2)*((i+1)!),i=0..floor_log_2(n)); end;
    floor_log_2 := proc(n) local nn,i; nn := n; for i from -1 to n do if(0 = nn) then RETURN(i); fi; nn := floor(nn/2); od; end;
    # next Maple program:
    a:= n-> (l-> add(l[j]*j!, j=1..nops(l)))(Bits[Split](n)):
    seq(a(n), n=0..57);  # Alois P. Heinz, Aug 12 2025
  • Mathematica
    a[n_] :=  Reverse[id = IntegerDigits[n, 2]].Range[Length[id]]!; Table[a[n], {n, 0, 60}] (* Jean-François Alcover, Jun 19 2012, after Philippe Deléham *)
  • PARI
    a(n) = if(n>0, a(n-msb(n)) + (1+logint(n,2))!, 0)
    msb(n) = 2^#binary(n)>>1
    {my(b = binary(n)); sum(i=1,#b,b[i]*(#b+1-i)!)} \\ David A. Corneth, Aug 21 2016
    
  • Python
    def facbase(k, f):
        return sum(f[i] for i, bi in enumerate(bin(k)[2:][::-1]) if bi == "1")
    def auptoN(N): # terms up to N factorial-base digits; 13 generates b-file
        f = [factorial(i) for i in range(1, N+1)]
        return list(facbase(k, f) for k in range(2**N))
    print(auptoN(5)) # Michael S. Branicky, Oct 15 2022

Formula

G.f. 1/(1-x) * Sum_{k>=0} (k+1)!*x^2^k/(1+x^2^k). - Ralf Stephan, Jun 24 2003
a(n) = Sum_{k>=0} A030308(n,k)*A000142(k+1). - Philippe Deléham, Oct 15 2011
From Antti Karttunen, Aug 19 2016: (Start)
a(0) = 0, a(2n) = A153880(a(n)), a(2n+1) = 1+A153880(a(n)).
a(n) = A225901(A276091(n)).
a(n) = A276075(A019565(n)).
a(A275727(n)) = A276008(n).
A275736(a(n)) = n.
A276076(a(n)) = A019565(n).
A007623(a(n)) = A007088(n).
(End)
a(n) = a(n - mbs(n)) + (1 + floor(log(n) / log(2)))!. - David A. Corneth, Aug 21 2016

Extensions

Name changed (to emphasize the functional nature of the sequence) with the old definition moved to the comments by Antti Karttunen, Aug 21 2016

A025494 Squares which are the sum of factorials of distinct integers (probably finite).

Original entry on oeis.org

1, 4, 9, 25, 121, 144, 729, 841, 5041, 5184, 45369, 46225, 363609, 403225, 3674889, 1401602635449
Offset: 1

Views

Author

Keywords

Comments

No other elements < 31!. - Paul.Jobling(AT)WhiteCross.com, Aug 10 2000
If there are any terms in either A014597 or A025494 beyond the last one given (i.e., n = 1183893 in A014597; equivalently n^2 = 1401602635449 in A025494), then n^2 must be greater than 48! (about 1.24139*10^61). - Jon E. Schoenfield, Aug 04 2006

Crossrefs

A059589 Sums of factorials of distinct integers.

Original entry on oeis.org

1, 2, 3, 4, 6, 7, 8, 9, 10, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 120, 121, 122, 123, 124, 126, 127, 128, 129, 130, 144, 145, 146, 147, 148, 150, 151, 152, 153, 154, 720, 721, 722, 723, 724, 726, 727, 728, 729, 730, 744, 745, 746, 747, 748, 750, 751, 752, 753
Offset: 1

Views

Author

Henry Bottomley, Jan 24 2001

Keywords

Comments

0! and 1! are treated as distinct.
From Bernard Schott, Apr 13 2017: (Start)
Factorial numbers (A000142) are included in this sequence.
Only one factorial (2!) is the sum of distinct factorials in more than one way: 2! = 0! + 1!.
(End)
Sequence contains the same nonzero terms as A059590, and in addition also each term immediately after each maximal run of consecutive terms in A059590. For example, because A059590 contains numbers 30, 31, 32, 33, this sequence contains the same four terms, and also 34 which follows them but is not included in A059590. - Antti Karttunen, Apr 15 2017

Examples

			128 is in the sequence since 5! + 3! + 2! = 128.
2 = 0! + 1!.
		

Crossrefs

Cf. A000142, A059590 (subsequences).

Programs

  • Mathematica
    Rest@Union[Plus @@@ (Subsets@Range[0, 6]!)] (* Ivan Neretin, Jun 05 2016 *)

A051761 Numbers that are simultaneously a sum of factorials of distinct integers and of the form a^b with b >= 2.

Original entry on oeis.org

0, 1, 4, 8, 9, 25, 27, 32, 121, 128, 144, 729, 841, 5041, 5184, 45369, 46225, 363609, 403225, 3674889, 1401602635449
Offset: 1

Views

Author

Paul.Jobling(AT)WhiteCross.com, Aug 10 2000

Keywords

Comments

0! and 1! are treated as distinct.

Examples

			4 is in the sequence since 2! + 1! + 0! = 4 = 2^2.
		

Crossrefs

Showing 1-4 of 4 results.