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.

Previous Showing 41-48 of 48 results.

A278225 Filter-sequence for factorial base (cycles in A060117/A060118-permutations): Least number with the same prime signature as A275725.

Original entry on oeis.org

2, 4, 12, 8, 12, 8, 60, 36, 24, 16, 24, 16, 60, 24, 24, 16, 36, 16, 60, 24, 36, 16, 24, 16, 420, 180, 180, 72, 180, 72, 120, 72, 48, 32, 48, 32, 120, 48, 48, 32, 72, 32, 120, 48, 72, 32, 48, 32, 420, 180, 120, 48, 120, 48, 120, 72, 48, 32, 48, 32, 180, 72, 48, 32, 72, 32, 180, 72, 72, 32, 48, 32, 420, 120, 120, 48, 180, 48, 180, 72, 48, 32, 72, 32, 120, 48, 48
Offset: 0

Views

Author

Antti Karttunen, Nov 16 2016

Keywords

Comments

This sequence can be used for filtering certain sequences related to cycle-structures in finite permutations as ordered by lists A060117 / A060118 (and thus also related to factorial base representation, A007623) because it matches only with any such sequence b that can be computed as b(n) = f(A275725(n)), where f(n) is any function that depends only on the prime signature of n (some of these are listed under the index entry for "sequences computed from exponents in ...").
Matching in this context means that the sequence a matches with the sequence b iff for all i, j: a(i) = a(j) => b(i) = b(j). In other words, iff the sequence b partitions the natural numbers to the same or coarser equivalence classes (as/than the sequence a) by the distinct values it obtains.

Crossrefs

Other filter-sequences related to factorial base: A278234, A278235, A278236.
Sequences that partition N into same or coarser equivalence classes: A048764, A048765, A060129, A060130, A060131, A084558, A275803, A275851, A257510.

Programs

Formula

a(n) = A046523(A275725(n)).

A278235 Filter-sequence for factorial base (digit levels): Least number with the same prime signature as A275735(n).

Original entry on oeis.org

1, 2, 2, 4, 2, 6, 2, 4, 4, 8, 6, 12, 2, 6, 6, 12, 4, 12, 2, 6, 6, 12, 6, 30, 2, 4, 4, 8, 6, 12, 4, 8, 8, 16, 12, 24, 6, 12, 12, 24, 12, 36, 6, 12, 12, 24, 30, 60, 2, 6, 6, 12, 4, 12, 6, 12, 12, 24, 12, 36, 4, 12, 12, 36, 8, 24, 6, 30, 30, 60, 12, 60, 2, 6, 6, 12, 6, 30, 6, 12, 12, 24, 30, 60, 6, 30, 30, 60, 12, 60, 4, 12, 12, 36, 12, 60, 2, 6, 6, 12, 6, 30, 6
Offset: 0

Views

Author

Antti Karttunen, Nov 16 2016

Keywords

Comments

This sequence can be used for filtering certain factorial base (A007623) related sequences, because it matches only with any such sequence b that can be computed as b(n) = f(A275735(n)), where f(n) is any function that depends only on the prime signature of n (some of these are listed under the index entry for "sequences computed from exponents in ...").
Matching in this context means that the sequence a matches with the sequence b iff for all i, j: a(i) = a(j) => b(i) = b(j). In other words, iff the sequence b partitions the natural numbers to the same or coarser equivalence classes (as/than the sequence a) by the distinct values it obtains.

Crossrefs

Other factorial base related filter-sequences: A278225, A278234, A278236.
Sequences that partition N into same or coarser equivalence classes: A060130, A257696 (?), A264990, A275806, A275948, A275964 (this is a proper a subset of the sequences that match with A278236).

Programs

Formula

a(n) = A046523(A275735(n)).
a(n) = A278234(A225901(n)).

A376886 The number of distinct factors of n of the form p^(k!), where p is a prime and k >= 1, when the factorization is uniquely done using the factorial-base representation of the exponents in the prime factorization of n.

Original entry on oeis.org

0, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 2, 1, 3, 1, 2, 2, 2, 1, 3, 1, 2, 2, 2, 2, 2, 1, 2, 2, 3, 1, 3, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 3, 2, 3, 2, 2, 1, 3, 1, 2, 2, 1, 2, 3, 1, 2, 2, 3, 1, 3, 1, 2, 2, 2, 2, 3, 1, 2, 1, 2, 1, 3, 2, 2, 2, 3, 1, 3, 2, 2, 2, 2, 2, 3, 1, 2, 2, 2, 1, 3, 1, 3, 3
Offset: 1

Views

Author

Amiram Eldar, Oct 08 2024

Keywords

Comments

See A376885 for details about this factorization.
First differs from A371090 at n = 2^18 = 262144.
Differs from A064547 at n = 64, 128, 192, 256, 320, 384, 448, 512, ... .
Differs from A058061 at n = 128, 384, 512, 640, 896, ... .

Examples

			For n = 8 = 2^3, the representation of 3 in factorial base is 11, i.e., 3 = 1! + 2!, so 8 = (2^(1!))^1 * (2^(2!))^1 and a(8) = 1 + 1 = 2.
For n = 16 = 2^4, the representation of 4 in factorial base is 20, i.e., 4 = 2 * 2!, so 16 = (2^(2!))^2 and a(16) = 1.
		

Crossrefs

Similar sequences: A064547, A318464, A376885.

Programs

  • Mathematica
    fdignum[n_] := Module[{k = n, m = 2, r, s = 0}, While[{k, r} = QuotientRemainder[k, m]; k != 0 || r != 0, If[r > 0, s++]; m++]; s]; f[p_, e_] := fdignum[e]; a[1] = 0; a[n_] := Plus @@ f @@@ FactorInteger[n]; Array[a, 100]
  • PARI
    fdignum(n) = {my(k = n, m = 2, r, s = 0); while([k, r] = divrem(k, m); k != 0 || r != 0, if(r > 0, s ++); m++); s;}
    a(n) = {my(e = factor(n)[, 2]); sum(i = 1, #e, fdignum(e[i]));}

Formula

Additive with a(p^e) = A060130(e).
Sum_{k=1..n} a(k) ~ n * (log(log(n)) + B + C), where B is Mertens's constant (A077761) and C = Sum_{p prime} f(1/p) = 0.12589120926760155013..., where f(x) = -x + (1-x) * Sum_{k>=1} A060130(k) * x^k.

A230417 Lower triangular region of A230415, a triangular table read by rows: T(n, k) tells in how many digit positions the factorial base representations (A007623) of n and k differ, where (n, k) = (0,0), (1,0), (1,1), (2,0), (2,1), (2,2), ..., n >= 0 and (0 <= k <= n).

Original entry on oeis.org

0, 1, 0, 1, 2, 0, 2, 1, 1, 0, 1, 2, 1, 2, 0, 2, 1, 2, 1, 1, 0, 1, 2, 2, 3, 2, 3, 0, 2, 1, 3, 2, 3, 2, 1, 0, 2, 3, 1, 2, 2, 3, 1, 2, 0, 3, 2, 2, 1, 3, 2, 2, 1, 1, 0, 2, 3, 2, 3, 1, 2, 1, 2, 1, 2, 0, 3, 2, 3, 2, 2, 1, 2, 1, 2, 1, 1, 0, 1, 2, 2, 3, 2, 3, 1, 2, 2, 3, 2, 3, 0, 2, 1, 3, 2, 3, 2, 2, 1, 3, 2, 3, 2, 1, 0, 2, 3, 1, 2, 2, 3, 2, 3, 1, 2, 2, 3, 1, 2, 0
Offset: 0

Views

Author

Antti Karttunen, Nov 10 2013

Keywords

Examples

			This triangular table begins:
  0;
  1, 0;
  1, 2, 0;
  2, 1, 1, 0;
  1, 2, 1, 2, 0;
  2, 1, 2, 1, 1, 0;
  1, 2, 2, 3, 2, 3, 0;
  ...
Please see A230415 for examples showing how the terms are computed.
		

Crossrefs

This is a lower, or equivalently, an upper triangular subregion of symmetric square array A230415.

Programs

  • Scheme
    (define (A230417 n) (A230415bi (A003056 n) (A002262 n)))
    (define (A230415bi x y) (let loop ((x x) (y y) (i 2) (d 0)) (cond ((and (zero? x) (zero? y)) d) (else (loop (floor->exact (/ x i)) (floor->exact (/ y i)) (+ i 1) (+ d (if (= (modulo x i) (modulo y i)) 0 1)))))))

Formula

a(n) = A230415bi(A003056(n),A002262(n)). [As a sequence, this is obtained by taking a subsection from array A230415.]
T(n,0) = A060130(n) [the leftmost column].
For n >= 1, T(n,n-1) = A055881(n) [the last nonzero column].
Each entry T(n,k) <= A231714(n,k).

A276002 Numbers n for which A060502(n) = 2; numbers with exactly two occupied slopes in their factorial representation.

Original entry on oeis.org

3, 7, 8, 10, 11, 13, 15, 16, 17, 20, 21, 25, 26, 28, 29, 30, 36, 38, 42, 43, 46, 47, 49, 50, 52, 53, 55, 56, 58, 59, 60, 62, 66, 67, 70, 71, 73, 75, 76, 77, 78, 80, 85, 87, 88, 89, 90, 91, 92, 93, 94, 95, 98, 99, 102, 103, 106, 107, 108, 109, 110, 111, 112, 113, 116, 117, 121, 122, 124, 125, 126, 132, 134, 138, 139, 142, 143, 144, 168, 174, 192, 194
Offset: 1

Views

Author

Antti Karttunen, Aug 16 2016

Keywords

Comments

Also numbers n such that A060498(n) is a two-ball juggling pattern.

Crossrefs

Formula

Other identities. For all n >= 1:
A060130(a(n)) >= 2.

A276003 Numbers n for which A060502(n) = 3; numbers with exactly three occupied slopes in their factorial representation.

Original entry on oeis.org

9, 27, 31, 32, 34, 35, 37, 39, 40, 41, 44, 45, 51, 57, 61, 63, 64, 65, 68, 69, 79, 81, 82, 83, 104, 105, 123, 127, 128, 130, 131, 133, 135, 136, 137, 140, 141, 145, 146, 148, 149, 150, 156, 158, 162, 163, 166, 167, 169, 170, 172, 173, 175, 176, 178, 179, 180, 182, 186, 187, 190, 191, 193, 195, 196, 197, 198, 200, 205, 207, 208, 209, 210, 211, 212
Offset: 1

Views

Author

Antti Karttunen, Aug 16 2016

Keywords

Comments

Also numbers n such that A060498(n) is a three-ball juggling pattern.

Examples

			27 ("1011" in factorial base) is included as there are three distinct values attained by the difference digit_position - digit_value when computed for its nonzero digits: 4-1 = 3, 2-1 = 1 and 1-1 = 0.
51 ("2011" in factorial base) is included as there are three distinct values attained by the difference digit_position - digit_value when computed for its nonzero digits: 4-2 = 2, 2-1 = 1 and 1-1 = 0.
57 ("2111" in factorial base) is included as there are three distinct values attained by the difference digit_position - digit_value when computed for its nonzero digits: 4-2 = 3-1 = 2, 2-1 = 1 and 1-1 = 0.
		

Crossrefs

Formula

Other identities. For all n >= 1:
A060130(a(n)) >= 3.

A331171 a(n) = min(n, A225901(n)), where A225901 is factorial base flip.

Original entry on oeis.org

0, 1, 2, 3, 2, 3, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 14, 15, 6, 7, 10, 11, 8, 9, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 48, 49, 52, 53, 50, 51, 66, 67, 70, 71, 68, 69, 60, 61, 64, 65, 62, 63, 54, 55, 58, 59
Offset: 0

Views

Author

Antti Karttunen, Jan 12 2020

Keywords

Comments

For all i, j:
a(i) = a(j) => A060130(i) = A060130(j).
For all i, j > 0:
a(i) = a(j) => A055881(i) = A055881(j).

Crossrefs

Programs

  • PARI
    A225901(n) = { my(s=0, d, k=2); while(n, d=n%k; n=n\k; if(d, s += (k-d)*(k-1)!); k=k+1); (s); };
    A331171(n) = min(n, A225901(n));

Formula

a(n) = min(n, A225901(n)).

A348138 For any number n with factorial base representation (d_1, ..., d_k), for i = 1..k, let f_i be the number of i's in (d_1, ..., d_k); the factorial base representation of a(n) is (f_1, ..., f_k).

Original entry on oeis.org

0, 1, 2, 4, 1, 3, 6, 12, 12, 18, 8, 14, 2, 8, 8, 14, 4, 10, 1, 7, 7, 13, 3, 9, 24, 48, 48, 72, 30, 54, 48, 72, 72, 96, 54, 78, 30, 54, 54, 78, 36, 60, 26, 50, 50, 74, 32, 56, 6, 30, 30, 54, 12, 36, 30, 54, 54, 78, 36, 60, 12, 36, 36, 60, 18, 42, 8, 32, 32, 56
Offset: 0

Views

Author

Rémy Sigrist, Oct 02 2021

Keywords

Comments

Leading zeros in factorial base representation of n are ignored.

Examples

			The first terms, in decimal and in factorial base, are:
  n   a(n)  f(n)  f(a(n))
  --  ----  ----  -------
   0     0     0        0
   1     1     1        1
   2     2    10       10
   3     4    11       20
   4     1    20        1
   5     3    21       11
   6     6   100      100
   7    12   101      200
   8    12   110      200
   9    18   111      300
  10     8   120      110
		

Crossrefs

Programs

  • PARI
    a(n) = { my (f=[]); for (r=2, oo, if (n==0, return (sum(k=1, #f, f[k]*(#f-k+1)!)), f=concat(f, 0); my (d=n%r); n\=r; if (d, f[d]++))) }

Formula

a(n) = n iff n = 0 or n is a factorial number (A000142).
A034968(a(n)) = A060130(n).
a(A153880(n)) = A153880(a(n)).
Previous Showing 41-48 of 48 results.