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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A295087 Distinct values in A002487 in the order of appearance.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 7, 8, 6, 9, 11, 10, 13, 12, 14, 15, 18, 17, 19, 21, 16, 23, 22, 26, 29, 25, 24, 27, 30, 34, 31, 20, 28, 33, 37, 32, 35, 41, 40, 47, 43, 44, 36, 39, 49, 46, 50, 55, 45, 38, 52, 51, 60, 53, 57, 48, 42, 56, 67, 63, 69, 76, 65, 61, 68, 58, 71, 64
Offset: 1

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Author

Rémy Sigrist, Nov 14 2017

Keywords

Comments

This sequence is a permutation of the nonnegative integers, with inverse A295088.

Examples

			The first terms of this sequence, alongside the first terms of A002487, are:
n   a(n)    fusc(k) k
--  ----    ------- --
1   0       0       0
2   1       1       1
.   .       1       2
3   2       2       3
.   .       1       4
4   3       3       5
.   .       2       6
.   .       3       7
.   .       1       8
5   4       4       9
.   .       3       10
6   5       5       11
.   .       2       12
.   .       5       13
.   .       3       14
.   .       4       15
.   .       1       16
.   .       5       17
.   .       4       18
7   7       7       19
.   .       3       20
8   8       8       21
.   .       5       22
.   .       7       23
		

Crossrefs

Programs

  • PARI
    fusc(n)=local(a=1, b=0); while(n>0, if(bitand(n, 1), b+=a, a+=b); n>>=1); b \\ after Charles R Greathouse IV at A002487
    s=0; for (n=0, 621, v=fusc(n); if(!bittest(s,v), print1(v", "); s+=2^v))
    
  • Python
    from functools import reduce
    from itertools import count, islice
    def A295087_gen(): # generator of terms
        s = {0}
        yield 0
        for n in count(1):
            if (m:=sum(reduce(lambda x,y:(x[0],x[0]+x[1]) if int(y) else (x[0]+x[1],x[1]),bin(n)[-1:2:-1],(1,0)))) not in s:
                yield m
                s.add(m)
    A295087_list = list(islice(A295087_gen(),20)) # Chai Wah Wu, May 18 2023

Formula

a(n) = A002487(A091945(n)).

Extensions

Formula adapted after change in A091945 by Rémy Sigrist, Dec 07 2022
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