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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A356148 a(n) is the number of positive integers whose binary expansion appears as a substring in the binary expansion of n or its complement.

Original entry on oeis.org

1, 2, 2, 4, 3, 4, 3, 6, 6, 4, 6, 6, 6, 6, 4, 8, 9, 9, 8, 8, 5, 9, 9, 9, 8, 8, 9, 9, 9, 8, 5, 10, 12, 13, 12, 12, 12, 10, 12, 12, 12, 6, 10, 12, 12, 13, 12, 12, 12, 12, 10, 12, 10, 12, 13, 12, 12, 12, 13, 12, 12, 10, 6, 12, 15, 17, 16, 17, 17, 16, 15, 17, 15
Offset: 1

Views

Author

Rémy Sigrist, Jul 28 2022

Keywords

Comments

Leading 0's in binary expansions are ignored.

Examples

			For n = 43:
- the binary expansion of 43 is "101011",
- it contains the positive numbers with binary expansions "1", "10", "11", "101", "1010", "1011", "10101", "101011",
- the complement of "101011" is "010100",
- it contains the positive numbers with binary expansions "1", "10", "100", "101", "1010", "10100",
- all in all, we have the following substrings: "1", "10", "11", "100", "101", "1010", "1011", "10100", "10101", "101011",
- so a(43) = 10.
		

Crossrefs

Programs

  • PARI
    a(n) = { my (b=binary(n)); #setbinop((i,j) -> my (s=fromdigits(b[i..j], 2)); if (b[i], s, 2^(j-i+1)-1-s), [1..#b]) }
    
  • Python
    def a(n):
        N = n.bit_length()
        c, s = ((1<> i)
                s.add((mask&c) >> i)
        return len(s - {0})
    print([a(n) for n in range(1, 74)]) # Michael S. Branicky, Jul 28 2022

Formula

a(n) >= A122953(n).
a(2^k-1) = 2^k-1 for any k >= 0.
a(2^k) = A004277(k) for any k >= 0.

A356150 a(n) is the sum of the positive integers whose binary expansion appears as a substring in the binary expansion of n or its complement.

Original entry on oeis.org

1, 3, 4, 10, 8, 12, 11, 25, 25, 18, 26, 28, 30, 33, 26, 56, 62, 61, 56, 56, 39, 63, 64, 67, 62, 66, 72, 77, 80, 78, 57, 119, 139, 143, 137, 135, 134, 119, 134, 134, 134, 81, 120, 138, 139, 147, 142, 146, 147, 148, 132, 153, 140, 157, 165, 165, 168, 174, 181
Offset: 1

Views

Author

Rémy Sigrist, Jul 28 2022

Keywords

Comments

Leading 0's in binary expansions are ignored.

Examples

			For n = 11:
- row 11 of A356149 is 1, 2, 3, 4, 5, 11,
- so a(11) = 1 + 2 + 3 + 4 + 5 + 11 = 26.
		

Crossrefs

Programs

  • PARI
    a(n) = { my (b=binary(n)); vecsum(setbinop((i,j) -> my (s=fromdigits(b[i..j],2)); if (b[i], s, 2^(j-i+1)-1-s), [1..#b])) }
    
  • Python
    def a(n):
        N = n.bit_length()
        c, s = ((1<> i)
                s.add((mask&c) >> i)
        return sum(s)
    print([a(n) for n in range(1, 60)]) # Michael S. Branicky, Jul 28 2022

Formula

a(n) >= A078823(n).
a(n) Sum_{k = 1..A356148(n)} A356149(n, k).
Showing 1-2 of 2 results.